Solved
There are a lot of potential reasons for this. If you have maintenance with PTC, you can send the traceback to PTC and they may be able to tell you the issue. They may also request the files
If it is a large assy, make sure you clean up model errors/warnings.
If it is PDMLink, you can try it in a new workspace.
It's pretty impossible to diagnose the real issue from what has been given.
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