About 1/2 of us have and it is the belt alright, tho probably not the tension but the alignment. Wheel needs alignment, as when it's out even slightly so is the belt. Do NOT use the marks on the swingarm to align it. I did and it destroyed the belt in time. Triumph warrantied it only because i told them i used the manual and went by the marks. How are they going to argue that oine when thier own manual is wrong !
Anyways, It needs to be done with a triumph tool which is a rod that goes thru the axl and is used with the little square nubs on the swingarm to align it. Many dealers may not have this tool or even know of it because the bird is the first belted triumph. Thats what I found anyways, so if you bring it to a dealer ask them about the tool and make sure they have it. Many bikes were delivered with the alignment out which is why so many had the chirp.