UE 5.6 Project Stuck at rc2.exe When Building

General Issues and Bug Reporting
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1

My UE 5.6 project gets stuck at rc2.exe for a very long time, and sometimes it won’t even open at all. Is there any way to fix this?

微信图片_20251227073757_257_42
微信图片_20251227073757_257_42605×340 20.2 KB

I have already modified the file located at
%AppData%\Roaming\Unreal Engine\UnrealBuildTool
with the following content:

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
	<WindowsPlatform>
    	</WindowsPlatform>
	<BuildConfiguration>
        		<bAllowUBA>false</bAllowUBA>
    	</BuildConfiguration>
</Configuration>

However, after restarting, it still didn’t work.

I also tried rebuilding the project in Visual Studio 2022, and the build output looks like this, and was stuck at Resource Default.rc2

Rebuild started at 8:06...
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.ScriptBuild\EpicGames.ScriptBuild.csproj (in 20 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Oodle\EpicGames.Oodle.csproj (in 30 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Mutable\Mutable.Automation.csproj (in 137 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.OIDC\EpicGames.OIDC.csproj (in 147 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Redis\EpicGames.Redis.csproj (in 151 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.ProjectStore\EpicGames.ProjectStore.csproj (in 170 ms).
Restored D:\Epic Games\UE_5.6\Engine\Plugins\ScriptPlugin\Source\ScriptGeneratorUbtPlugin\ScriptGeneratorUbtPlugin.ubtplugin.csproj (in 42 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Perforce.Fixture\EpicGames.Perforce.Fixture.csproj (in 187 ms).
Restored D:\Epic Games\UE_5.6\Engine\Intermediate\Build\BuildRulesProjects\MarketplaceRules\MarketplaceRules.csproj (in 214 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\CrowdinLocalization\CrowdinLocalization.Automation.csproj (in 61 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Android\Android.Automation.csproj (in 110 ms).
Restored D:\Epic Games\UE_5.6\Engine\Intermediate\Build\BuildRulesProjects\UE5Rules\UE5Rules.csproj (in 296 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Turnkey\Turnkey.Automation.csproj (in 180 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\TVOS\TVOS.Automation.csproj (in 191 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\LowLevelTests\LowLevelTests.Automation.csproj (in 201 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\SteamDeck\SteamDeck.Automation.csproj (in 252 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\SmartlingLocalization\SmartlingLocalization.Automation.csproj (in 95 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Linux\Linux.Automation.csproj (in 146 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\OneSkyLocalization\OneSkyLocalization.Automation.csproj (in 67 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Scripts\AutomationScripts.Automation.csproj (in 78 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Perforce\EpicGames.Perforce.csproj (in 151 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Localization\Localization.Automation.csproj (in 187 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\BuildGraph\BuildGraph.Automation.csproj (in 196 ms).
Restored D:\Epic Games\UE_5.6\Engine\Intermediate\Build\BuildRulesProjects\UE5ProgramRules\UE5ProgramRules.csproj (in 409 ms).
Restored D:\Epic Games\UE_5.6\Engine\Platforms\VisionOS\Source\Programs\AutomationTool\VisionOS.Automation.csproj (in 206 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\LiveLinkHub\LiveLinkHub.Automation.csproj (in 80 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\CookedEditor\CookedEditor.Automation.csproj (in 134 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Mac\Mac.Automation.csproj (in 121 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.AspNet\EpicGames.AspNet.csproj (in 2 ms).

Failed to restore D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Gauntlet\Gauntlet.Automation.csproj (in 13 ms).

Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Core\EpicGames.Core.csproj (in 8 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Build\EpicGames.Build.csproj (in 4 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Apple\Apple.Automation.csproj (in 18 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.csproj (in 80 ms).

Failed to restore D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\AutomationUtils\AutomationUtils.Automation.csproj (in 21 ms).

Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Slack\EpicGames.Slack.csproj (in 63 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Perforce.Managed\EpicGames.Perforce.Managed.csproj (in 489 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.BuildGraph\EpicGames.BuildGraph.csproj (in 80 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Serialization\EpicGames.Serialization.csproj (in 14 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.MsBuild\EpicGames.MsBuild.csproj (in 495 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Tracing\EpicGames.Tracing.csproj (in 60 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.UBA\EpicGames.UBA.csproj (in 97 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.IoHash\EpicGames.IoHash.csproj (in 7 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Win\Win.Automation.csproj (in 97 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\Insights\Insights.Automation.csproj (in 97 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\IOS\IOS.Automation.csproj (in 135 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\XLocLocalization\XLocLocalization.Automation.csproj (in 103 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Horde\EpicGames.Horde.csproj (in 10 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.UHT\EpicGames.UHT.csproj (in 34 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.MongoDB\EpicGames.MongoDB.csproj (in 30 ms).

1>------ Rebuild All started: Project: EpicGames.UBA, Configuration: Development Any CPU ------
2>------ Rebuild All started: Project: EpicGames.Oodle, Configuration: Development Any CPU ------
3>------ Rebuild All started: Project: EpicGames.OIDC, Configuration: Development Any CPU ------
4>------ Rebuild All started: Project: EpicGames.Core, Configuration: Development Any CPU ------

Restored E:\UnrealProjects\UGhostPark\Intermediate\Build\BuildRulesProjects\UGhostParkModuleRules\UGhostParkModuleRules.csproj (in 157 ms).
Restored D:\Epic Games\UE_5.6\Engine\Source\Programs\AutomationTool\AutomationTool.csproj (in 160 ms).

NuGet package restore failed. Please check the "Error List" window for detailed warnings and errors.

EpicGames.Oodle -> D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Oodle\bin\Development\net8.0\EpicGames.Oodle.dll
EpicGames.UBA -> D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.UBA\bin\Development\net8.0\EpicGames.UBA.dll
EpicGames.Core -> D:\Epic Games\UE_5.6\Engine\Source\Programs\Shared\EpicGames.Core\bin\Development\net8.0\EpicGames.Core.dll

Warning NU1903: Package "Microsoft.Build" 17.11.4 has a known HIGH severity vulnerability.

Using bundled DotNet SDK version: 8.0.300 win-x64
Running UnrealBuildTool:
dotnet "..\..\Engine\Binaries\DotNET\UnrealBuildTool\UnrealBuildTool.dll"
UGhostParkEditor Win64 Development
-Project="E:\UnrealProjects\UGhostPark\UGhostPark.uproject"
-WaitMutex -FromMsBuild -architecture=x64 -Rebuild

Cleaning UGhostParkEditor binaries...
Creating makefile for UGhostParkEditor (no existing makefile)
Building UGhostParkEditor...

Using Visual Studio 2022 14.38.33145 toolchain
Windows 10.0.22621.0 SDK

Using Unreal Build Accelerator (UBA)
UbaServer listening on 0.0.0.0:1345

------ Building 12 action(s) started ------
[1/12] Resource Default.rc2

I even attempted to modify the project’s **Config/**DefaultEngine.ini file, but none of these approaches helped.

[BuildSettings]
bUseUnrealBuildAccelerator=false
bUseUBTMakefiles=false
bAllowFASTBuild=false

My compiler/toolchain version is MSVC 14.38.33145，I suspect this might be related to UBA.
Does anyone know how to fix this?

2

hi @u9king

Looks like have UE Revision Control enabled on your project, perhaps even Perforce

Using Perforce as Source Control for Unreal Engine | Unreal Engine 5.7 Documentation | Epic Developer Community

rc2.exe is UE Revision Control , but usually called urc.exe

Epic UE Fortnite support posted a temporary fix for UEFN problems.

Unreal Revision Control error: Failed to load fragment payload - General / Issues and Bug Reporting - Epic Developer Community Forums

1 Like
3

I have fixed the problem and hope this helps others in the future.
Compile time has been reduced from 20 minutes to just 1–2 minutes.

Edit:

1.<PROJECT_DIR>\Saved\UnrealBuildTool\BuildConfiguration.xml

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
    <BuildConfiguration>
        <bAllowUBAExecutor>false</bAllowUBAExecutor>
    </BuildConfiguration>
</Configuration>

By the way,I also tried changing only the WindowsSdkVersion, but it didn’t help.

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration"><WindowsPlatform>
    <WindowsSdkVersion>10.0.22621.0</WindowsSdkVersion>
</WindowsPlatform>
</Configuration>

And earlier, I also tried adding the configuration to
%APPDATA%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml, but that didn’t work either.

In the end, the following attempts did NOT work:

  • Modifying %APPDATA%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml

  • Changing the WindowsSdkVersion 10.0.22621.0

  • Adding the engine path and project path to the Windows antivirus whitelist

  • Verifying engine installation and Visual Studio2022

  • Rebuilding project files manually from .uproject

  • Running UE and Visual Studio as administrator

Thx to everyone above for the helpful replies.