"it crashes when I place the WMB in a different level that is not empty"
- that's right!

Sorry, no crash either.

Maybe the bad file is in your main level, not in the map entity? Check the other entities that you've placed in that level.

If you can't find the problem, I can look into it - but please upload the really crashing project then.

This is the minimum that makes the level crash when the wmb and a model come into view:

http://www.puppenheim.org/gartenhauswmbtest.zip

Very weird! The model has a simple action assigned called vegetation, if the model gets no action assigned, everything works, but with an action assigned, it crashes.

Just open test.wmp in WED and run the level, the assigned script just loads the level and got a dummy action called vegetation.

Thanks - I could now finally reproduce the problem. It's indeed a bug, and will be fixed in the next update. It only happens in a rare combination of circumstances.

Good to hear that the searching could serve its purpose.