WD Passport Pro 3TB/4TB - Excessive indexing / thumbnail rebuilding?

I have two My Passport Wireless drives which have 35,000 + music files plus artwork images. These have both been working fine up until about 2 / 3 months ago.

Both drives now are constantly indexing / building thumbnails which then prevents me from using these devices a portable media servers.

I have tried leaving them on rebuilding ( for days and days ) but rebuild never seems to stop ( making sure Plex or Twonky is off ).

I have run both quick check / full check. No errors reported.

I have factory reset the devices including wiping the data. I can reload the data onto the device and the initial indexing runs ( it takes a while but does complete ) but after about two to three weeks the problem comes back.

Only thing I can find on line is to login as device under SSH and either kill the tasks every time or change permissions on the index / thumbnails so device can’t update them … but logging onto SSH invalidates warranty and one of my drives still under warranty.

Any other suggestions ?