PLEX suddenly not working on two of my three Mini's...

PLEX app suddenly stopped working on two of my three Mini's pretty much since Yesterday.
All three Mini's are on the same FW:
20.1.1a.RC10-01-6-A92
All hardwired cat5, all working flawlessly for months.


On failed Mini's, the Plex app takes 2-3x longer than normal to load, then I get a Message: "Plex has encountered an error <snip> press button to factory reset PLEX" So I've done that several times, entered the new PLEX PIN on the PLEX Link site- PLEX starts booting on the Mini, takes 2-3x longer than normal to load- and it goes right back to the "Plex has encountered an error- press button to factory reset PLEX" screen again.

Remedies tried:
Reboot all Mini's
Reboot Roamio
Net-connected all Tivos
No "pending restarts" found on any units


Moved the one working PLEX/Mini to the locations of the non-working PLEX/Mini's ad it works properly in both locations. Moved both non-working PLEX/Mini's to the location where the one Mini was working- PLEX still not working on either one of them. So it's not a network/switch problem.

Has Tivo recently broken something in their PLEX app?