Hi @montgjoa, that's interesting
How are you copying the assignments over ? I've just copied using the 'Copy To' function from the source course to the target source without any issues.
This appears to have maintained fidelity with the original - however from previous experience this doesn't work the same as a course import, and 'Copy To' may not take any linked content across and transpose the file destinations, so may not be a suitable solution.
We no longer have access to import assignments in our SIS based assignments, but perhaps someone else on the forum can check whether they have the same import experience as yours.
Good luck !