So to repro I have a UMG widget child in the designer marked as a variable named SomeChild
I use this variable in some blueprint
Next I decide to replace the widget with a different type of widget. It deletes the variable, probably because my variable is no longer the same type.
I Mark the child as a variable again and type in the same variable name for it. Editor crashes after I try to compile or click something else.
In the C++ the error message says something about renaming over an existing object.
I have to restart the editor to ensure that after I replace my widget that I can rename it back to its original variable name without the editor crashing.