Editor crashes after trying to migrate asset

I tried to migrate some assets from one project into another, unfortunately the assets left uassets that couldnt be opened in the destination project.

Now I’m trying to open the original project (months of work) and it causes a fatal crash every time, I’m in deep trouble if I cant resolve this and get this project to work.

Can someone please help? I maybe looking for a new job if I can’t get this to work!

The logfile is stating:
[2017.05.27-19.20.40:108][ 0]LogCrashTracker:

[2017.05.27-19.20.40:111][ 0]LogWindows: Windows GetLastError: The operation completed successfully. (0)
[2017.05.27-19.20.40:111][ 0]LogThreadingWindows:Error: Runnable thread RenderThread 2 crashed.
[2017.05.27-19.20.40:111][ 0]LogCrashTracker:

[2017.05.27-19.20.40:111][ 0]LogWindows:Error: === Critical error: ===
Assertion failed: (GIsCriticalError || !NumMarks) [File:D:\Build++UE4+Release-4.12+Compile\Sync\Engine\Source\Runtime\Core\Public\Misc\MemStack.h] [Line: 72]

Crash in runnable thread RenderThread 2

[2017.05.27-19.20.40:112][ 0]LogWindows: Windows GetLastError: The operation completed successfully. (0)
[2017.05.27-19.20.40:112][ 0]LogWindows:Error: HandleError re-entered.
[2017.05.27-19.20.40:112][ 0]LogWindows: FPlatformMisc::RequestExit(1)
[2017.05.27-19.20.40:112][ 0]Log file closed, 05/27/17 20:20:40

I’ve attached a log file.
I’d REALLY appreciate some help!
link text