Hmm , very strange, check these issues
1) pallet fork is not touching the underside of the roller table when balance is screwed down
2) Check the balance staff is true and not bent at the pinions, if your removing the balance from the [censored] to check this, remove the hairspring and collet also and check the balance in the movement without pallet fork for rotational freedom
3) Balance jewels are the correct ones, I am presuming no changes have been made
4) Has the balance [censored] been cleaned, could it have been bent slightly on cleaning, there is a way of overcoming this
5) Curb pins are not frictionally holding the hairspring
6) Hairspring is flat to the balance wheel and definitely not touching either the balance wheel or the underside of the [censored]
7) Check for rundown. let the movement down, remove balance, remove pallet fork and bridge, wind the movement only three or four turns. Watch carefully the escape wheel. As the watch runs down it should at the end of the power run slightly in reverse, so the escape wheel changes rotational direction. If the escape wheel stops dead and does not "reverse" there may be other issues. This is a common service test and should always be carried out. It gives you a very good insight into amplitude and power reserve.
Oops, forgot to add, I think you issue is the balance [censored] being bent downwards