indesign refuses to change fonts in documents

I manage a number of creative cloud users. And I have one user who cannot change fonts within any of his documents. ALL users are running the latest version of indesign, 17.2.1, and th latest version of macOS, 12.4 and using the latest version of FontExplorer, 7.3 with a font server. And the indesign files are worked on locally, not from a network or cloud-based server. 

This one user cannot change fonts withing any of his indesign documents. The fonts are not missing and are activated correctly from the font server. All he is attempting to do is change the font from one font to another, or change it from one weight to another. What he can do is use the eye dropper tool on text using the font he wants to change to and that changes the font correctly. But if he chooses the font in the menu it will not change fonts! It remains whatever font it was. Like, he's able to select the font in the menu, but it changes back to whatever the existing font is. He's resorted to keeping a document on his laptop where he applies the font he wants because it's all working fine on his laptop, then emailing the file to himself and opening it on his imac and using the eyedropper to style his fonts.

I have reset his indesing preferences and it worked fine for a short time while I tested it. but then the next time he used it, it was happening again for him. so then I deleted all the caches, and again it worked fine while I tested it then when he began working again it stopped working for him. I'm about to try unistalling and reinstalling indesign which might help a little. But I'm doubtfull that it will stick. I cannot find anything about this being a known issue or other users having this issue! All I can find is artcles about font conflicts or missing fonts, etc. which are not the same as my problem. Is there anything else I can do to troubleshoot and hopefully fix this?