Looks like I solved the problem. I had to change two things for the crashes to disappear:
- When constructing the UBodySetup for my mesh I have to set bMeshCollideAll = false, which is weird because it is set to true in every piece of code I find about procedurally generating meshes (for example A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums)
- When creating the FTriMeshCollisionData for my mesh I set the wrong material indices for the physics collision material. I still do not know how I can reference my physics materials here and what that index actually represents, because any index other than 0 leads to a crash.
Thank you Tim for the support!