Fatal error! Unhandled Exception: EXCEPTION_ACCESS_VIOLATION writing address 0x0000000000000208

It looks like a function was renamed between 4.26 and 4.27.
Guess you’re not using C++? If this is the Launcher version of Unreal you can install the optional Engine Source and Editor Symbols for Debugging and that error would show you exactly where the problem is. As in which line and in which line.

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