Multiple bugs in existing issues/merge requests after project transfer

Summary

After a project is transferred, I found out there are some bugs regarding the existing issues and MRs.

Steps to reproduce

1. Have some issues and WIP MRs open in a project.
2. Transfer to a new group.
3. Find an issue with a milestone and attempt to edit its issue description.
4. Find an MR with a milestone and attempt to toggle it as WIP. Then attempt to close it.

Example Project

• gitlab-docs#310 (closed) - Cannot edit the description, check the checklist.
• gitlab-docs!486 (closed) - Cannot toggle WIP or close the MR.

What is the current bug behavior?

For items with a milestone inherited from the previous group:

• Cannot edit issue description
• Cannot toggle WIP from MRs
• Cannot close MRs
• MR merged, but the MR didn't enter merged status gitlab-docs!409 (comment 191646742)

What is the expected correct behavior?

Inverse of the above.

Output of checks

This bug happens on GitLab.com