That’s unusual unless its a cheap x-ring… Was it D.I.D.? If so that’s really odd as I got 24,000 miles out of a D.I.D x-ring and probably adjusted it 20 times - 15 of those being in the last 500 miles of it’s life
is he over adjusting the chain ?..Ive known people to adjust a chain on the main stand,so when the bike sits on the road the free play in the chain almost disappears thus stretching the chain !
Some chains on some bikes do that. Try running it slightly slack … only an extra half inch of slack though. If it stays at that tension, then leave it.
My ZX12R has this strange characteristic, so the chain runs with slightly more play than manual says to run, but I never need to adjust it. If I tightened it up, it would do just as you described.
Its a gold DID X-ring. Thanks for all the ideas, putting it down to just the bike tbh. Hes not over adjusting it, and cant think of anything else it could be right now.