Update:
I did find out that substepping seemed not to be the only problem but it made it worse!
Certain maps in the project do build without substepping enabled while others still create the mentioned fatal error.
BUT with substepping enabled it does not matter which maps I include in the build it will fail with the mentioned fatal error.
So, the question is still to be answered, how does this error be even possible while cooking/packaging? Why do certain phyiscs be updated at cook time?
best regards