Issue with Relinking Missing Files

I am building a program by inserting a segment each week. For the past three weeks I am getting a group of 5-8 clips that go missing on the timeline within 24-48 hours after inserted. When I select the missing clip red icons and open the relink window, no media files show up. I then have to re-import the files to a new event and then replace the red icons with those files.
I am running system 11.4 on a new Mac Pro. Media files are on a separate internal SSD.     Previous programs had no issues.  

Are all files (library, media, etc) on drives that are formatted APFS or Mac OS Extended Journaled (aka HFS+)? If any are on ExFAT or other partition types it might cause problems.

If you select a red timeline clip, then do SHIFT+F, it will locate that in the event browser. IF that is red, and you select that one clip, then do File>Relink Files>Original Media, it should list the file (if missing).

If it's not missing (ie not listed in the "relink original files" box), select the "All" button and it will show the current expected location in gray letters just below that box. THAT is where it thinks the file is. Go there in Finder and make sure the file is present and it's on a locally-attached hard drive (not a network drive) formatted APFS or HFS+.

Make sure there is no permissions issue and FCP has access to that drive and folder. Go to Mac System Preferences>Security & Privacy>Privacy tab, in the left column select Full Disk Access and in the right column make sure FCP is granted that access.

Also check whether it's the issue described by Ben Halsall, "Fixing missing clips on the timeline".

SSD is correctly formatted. Selecting in the timeline or browser makes no difference, the relink window comes up empty. This does not sound like a normal missing link problem and the fact that it has always been 5-8 clips in a row go missing is strange. I never rename files or alter then in any way.
I did select FcP in Privacy and will see if that makes any difference.
Thanks for your comments.