Crash on build startup - "Cast of nullptr to ScriptStruct failed"

Hello, I have this error when I execute my build I packaged for Windows 32 bits.
It opens normally in full screen with the black background and then drops a windows with this:

Fatal error:
[File:D:\Build\++UE4+Release-4.18+Compile\Sync\Engine\Source\Runtime\CoreUObject\Private\Templates\Casts.cpp] [Line: 10]
Cast of nullptr to ScriptStruct failed

This error started in version 4.18.2, so I decided to update to 4.18.3, but the error is still there.

Before this I was able to build with no problems in 4.18.2, so I don’t know what hapend here. Any ideas?

I upgraded to 4.18.3 as well. I have been trying to figure this problem out for the last three days. I have isolated my crash to occur in one of my UMG widgets. I wish I could figure out why.

Almost the entire callstack is in UObject.

Nuts!

I found the event that was being called immediately before the crash. The event called a function, UpdateColorOfHealthBar, which called a function on multiple widgets.

I put in logging immediately after the event and within the UpdateColorOfHealthBar function.

I then cooked again, ran the cooked build and noticed only my first log immediately after the event was hit. I then inlined the blueprint function manually. (why? don’t know, ran out of ideas of things to do)

Somehow this resolved my crash in the most unsatisfying way possible. I don’t know why the crash was occurring or why my fix worked or if it will break again.