Declare any damage previous to the judges pre-match and then that damage can't be counted against you points wise under damage. If it buggers up the operation of the machine then tough titty. Nice and simple.

So if you have a spinner that isn't going to spin or a flipper that won't flip then the judges know it before hand and can discount that from the point scoring. If your wheel doesn't work well then it's much the same and likely to hamper your chances of winning the match.