If you develop with source code via GitHub, you can already integrate the fix for the blueprint compile crash here (must be signed into GitHub account): https:///EpicGames/UnrealEngine/commit/38457aec8e69e7423b6f606dc9ac22a8e63e2635
If you are a binary user via the Epic Games Launcher, then thank you for your patience while we work to release a new build as quickly as we can (with quality-testing, etc).
Concerning the severity of this BP bug, is it likely to assume that the 4.12.2 hotfix will be released sooner than next week around the usual time?^^
[=;544268]
Concerning the severity of this BP bug, is it likely to assume that the 4.12.2 hotfix will be released sooner than next week around the usual time?^^
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Yes, we are pushing to release 4.12.2 as soon as possible. It should be available this week.
Quick note for those experiencing the same problem while the fix rolls out - There doesn’t seem to be an compiling when the program opens so I am able to keep working, changing variables - saving changes then restarting project. its slow yes, and annoy - double yes, but its better than being stuck in dev limbo 
Mine crashes also when i compile and even when i press play…
I get random crashes while play in editor
UPDATE!
The 4.12.2 Hotfix is now live! This hotfix resolves a critical crash when refreshing blueprint dependencies on a blueprint with no class, as well as fixing 10 other important issues.
Please be aware that after updating to this hotfix, it will be necessary to recompile shaders on your projects.
If you experience a bug with the 4.12.2 Hotfix, please remember to log a bug report for the on the UE4 AnswerHub to the Bug Reports section.
Fixed in 4.12.2
Fixed! UE-31740 Crash While Compiling Blueprint in FBlueprintEditorUtils::RefreshExternalBlueprintDependencyNodes()
Fixed! UE-31655 BP EQS generators crash on adding vectors.
Fixed! UE-31723 Attempting to build MinidumpDiagnostics with Visual 2015 Update 2 results in failure
Fixed! UE-31612 Physics enabled Child Actor components that spawn with with a delay, always spawns at world origin
Fixed! UE-31680 [CrashReport] DestroyChildActor->Rename->StaticFindObject()
Fixed! UE-31682 [CrashReport] UE4Editor_CoreUObject!UObjectBaseUtility::GetOutermost() [uobjectbaseutility.cpp:118]
Fixed! UE-31736 SteamController BackRight is not setup correctly
Fixed! UE-29543 Adjusting Light Source Radius/Length creates undesirable effect
Fixed! UE-31589 Capture reflections on translucent materials are broken
Fixed! UE-31715 Static Meshes Disappear with Media Player Asset Applied as Material in Standalone or Packaged Game
Fixed! UE-31687 Vive: Positional Latency with a Possessed Pawn’s Camera Component
****! Put 31679 in there 
[= Ellis;544916]
UPDATE!
The 4.12.2 Hotfix is now live! This hotfix resolves a critical crash when refreshing blueprint dependencies on a blueprint with no class, as well as fixing 11 other important issues.
Please be aware that after updating to this hotfix, it will be necessary to recompile shaders on your projects.
t
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Thank you!
Thanks, real lifesaver!
Thanks for the fix!
Thank for the quick fixes :D, I was using the source version of the engine for the pass day.
Awesome Epic. I love the speed of the hotfixes =) These crashes were a bit annoying 
[=Filly_The_Owl;544929]
****! Put 31679 in there 
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Kind of hard to do when a fix hasn’t been submitted just yet.
In all seriousness, it’s only been submitted for a couple of days and still needs to be investigated.
Since the Update to 4.12.2 my mouse behaves really weird. Relatively often when I drag around stuff in BP (Nodes, pins etc.) my mouse looses focus of the current operation, feels like it detects a double click. I’m not entirely sure if this is related to the Update or just coincidence and my mouse started failing. Please let me know if anybody experiences something similar (I have been mainly working in UMG, FPS capped at 25).
I can’t “Submit to source control” using the git (beta) plugin which is integrated in UE4.12. I get
Error fatal: Not a git repository: ‘C:/Program Files (x86)/Epic Games/4.12/Engine/Content/.git’
EditorErrors:Warning: Warning Failed checking source control status!
But the developer of the plugin seems to have submitted the fix for it as a pull request on github:
https:///EpicGames/UnrealEngine/pull/2484
[=Abhijeet;545025]
I can’t “Submit to source control” using the git (beta) plugin which is integrated in UE4.12. I get
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I am sorry for this serious regression of the Git plugin I introduced! It is only present on binary builds, not on source build from a clone of Github (because it rely incorrectly on Engine/ being under a git repository).
But there is another serious regression of the Git plugin; the Visual Diff is not working on 4.12! I’ve also posted a pull request for this one: Git plugin: Fix for Git diff not working in UE 4.12 (and ) #2406.
I know that it is not as critical, as it’s not a crash, and only a fraction of people are using the Git plugin…
But on the other way, there is no risk in integrating changes on the plugin in 4.12, only risks for the plugin itself.
Cheers!
So git plugin simply won’t work until 4.13? Or pull request could make it into 4.12.3?
No more crashes, thanks for the quick fix for the quick fix 
One I am having is lots of my shaders are recompiling far too frequently, even with the smallest changes. I can’t seem to reproduce it in a new project, I expect it’s old baggage from my project.
Epic there is a game and engine breaking bug that I pointed out during release 5, and yeah I should of posted it on answerhub before posting in the threads but please look at it… Additional windows drop their FPS while in focus instead of out of focus - Platform & Builds - Unreal Engine Forums