I've had a similar thing happen to my TA05. Something got stuck in the pulley, flipped the belt over and wore out the centre pulley. If I could find a centre pulley that was metal I'd get it as my local hobby shop can't get the centre pullies (NFI why, they can get part #51212 and #51214 but not 51213) so I had to order it online.
Oh, and if you think changing and adjusting the belts in a TA05 is annoying, try doing a TRF415. You'll soon learn to appreciate how easy the TA05 is.