I was brave and returned my oticon more 1s back and went to a different Audiologist
I now have a pair of Phonak lumity life90s.
I have had them a week and they have been absolutely fine.
My guitar sounds fine(and probably better) and I haven't needed to use a specific music program (the aids do it automatically). I am very happy so far. I don't know whether that will change when they are turned up full volume - they are currently on 80%. So far I think I will be very happy with my phonaks where the issue with the oticons was really quite upsetting. It could be that the oticons were faulty but suspect not.
Good luck and feel free to ask for an up date