Bridge CC 2019 Preview Panel does not show preview

Hi, 

Bridge CC 2019, Preview Panel will sometimes not show the previews for some TIFF files.

Will only show TIFF file icon. Metadata for camera settings when shot, will be blank.

It apprears to be random, some files previews render fine some not. 

When edit these files in Photoshop and saved, then the preview will render in Bridge, Metadata is restored. But upon quitting Bridge and relaunching, the preview no longer appears and reverts back to showing TIFF icon.

Reset Preferences, Purged Cache for all files will render previews fine. But again, upon quitting Bridge and relaunching, reverts back to showing TIFF icon.

Seems to do fine with JPGs.

Updated to Bridge CC 2020, same problem.

Searching online, cannot find anyone else with this problem.

System is Mac OS Mojave 10.14.6  

Any suggestions?

Thanks in advance.