[AMc]

Seems unlikely that Tivo would add a destructive update to the IR codes.
Have you checked for remotes with buttons pressed, video senders, laptops, low energy light bulbs etc. that may be sending a continuous IR signal. Tivo will wait until it 'goes quiet' before sending IR commands.

You can check if the front blaster is firing with a digital camera/camera phone - send a channel change command with the Tivo remote and a moment later you should see a purple dot in the black window on the Tivo (through the viewfinder of the camera) which is the blaster firing the remote control code.

 

[AMc]

Well if it's 3 tivos & 3 STBs then either Tivo has updated their codes or Panasonic has updated their box - hard to say which as both are pretty unlikely.
My only suggestion would be to try some other Panasonic codes and/or freeview codes on Tivo to see if you can find an alternative that also works...very odd.

 

[AMc]

Glad you got it sorted - what a weird set of coincidences!
It's interesting that the recent Sky C4+1 problems with DECT and your issue here show that all this 'free for all' band wireless equipment has some unexpected issues when working in the same environment.