Can't launch Editor after Unparenting BP Class

Actually the questions says it all, more or less. From time to time I get this weird bug, that the details of components are not visible in Blueprints deriving from C++ Classes which declare and define these components. Ususally I get this fixed by creating the same Subclass as Blueprint and voila: details visible again (if someone has a fix for that, that would be even greater, but its not the actual question).

Now I wanted to unparent my Blueprint, and parent it again to the C++ Class, hoping that all my variables in my BP would stay existent… Sadly, I got a Crash right after unparenting (did not save the log, was a while ago) and I am not able to get back into the engine, no matter which way of starting I use.
The error message always is:

Assertion failed: InElementOwner [File:D:\build\++UE5\Sync\Engine\Source\Runtime\TypedElementFramework\Public\Elements\Framework\TypedElementOwnerStore.h] [Line: 131] Element owner passed to RegisterElementOwner was null for key (<GetTypedElementOwnerStoreKeyDebugString not implemented for key type>)! Element owners must be valid!

What am I supposed to do? I highly suspect my BP Class of beeing the good-for-nothing, because it has no parent at the moment, which of course, is not very good.
Can I delete the BP somehow from outside of the editor?

If it’s blueprint only - there should be a physical file in your project with that name - are you able to delete that (making a backup first)?

I had this exact same bug with the child blueprints not showing components created in the c++ parent. My workaround was to just comment out the UPROPERTY associated with the component in my parent header file then run it then uncomment out the UPROPERTY and it would work (The component would now be visible in my child BP).

But now i’ve run into this same error that you have, did you manage to solve it?

I’ve got the same error when use NewObject in ActorComponent to create antoher one component inside (UE 5.3, C++). I fixed it by using CreateDefaultSubobject