UE 5.6 Project Stuck at rc2.exe When Building

u9king
Sat, 27 Dec 2025 01:11:13 +0000
Issues and Bug Reporting

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?

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?

3 posts - 2 participants