As a general principle, yes, of course you can.

I’m never worried about equipment having been looked at by others, only about whether others have damaged it. Unfortunately, certain individuals are known to do such poor work so regularly that I may decline to work on equipment they’ve touched. This can be most easily established through an inspection and discussion with the equipment owner.

Why? Because the damage inflicted often renders further work difficult or even impossible in the worst cases. I’ve had to give that news often, and it’s never well received. It’s not fair for me to have to repeatedly give that news, and even less fair for these issues to become mine, or the next repairer’s problem.

You’ll see the dilemma from the perspective of a business that helps people; you want to help on the one hand, but you don’t want to dig a hole for yourself with gear that has been ruined by others. It’s a tricky one and something I deal with case by case.