As a general principle, of course.

I’m never worried about equipment having been looked at by others, only about whether it has been damaged by others.

Unfortunately, certain individuals are known to do such poor work so regularly that I may decline to look at the equipment they’ve touched. Why? Because the damage inflicted often renders further work difficult, not viable or even impossible in the worst cases.

It’s not reasonable for these issues to become mine, or the next repairer’s problem, and unfortunately, all good repairers will know what I’m talking about. If circuit boards have been destroyed, for example, I will often decline to work on a piece of equipment.