FCPX and PHOTOS: random ‘media not found’ issue

Hello.

In PHOTOS, I created a new photo library to hold only certain content.

I imported my vacation photos into that library - a mix of stills and videos.

I created new library in FCPX and created new project.

The content from the new photos library is visible in FCPX photos browser.

RANDOM PROBLEM: occasional photos selected and reviewed in browser then dragged into timeline become “media not found” items.

Any suggestions welcome. CPU is 2020 M1 running OS 12.6.2 PHOTOS v. 7 and FCPX 10.6.6