Do shops ever fix something on the first try?

With a 1975 rig, it's getting harder to find shops that have employees who know how to work on non-electronic engines. But fortunately, I have one shop with a mechanic who knows my rig and understands it (as done the owner) and so things go well. But there is always a weird issue that throws them once in a while.

I've also found that out on the road, there is usually someone (of any age) who hobbies with these old engines and can provide advice/assistance. They just don't work as mechanics in shops because they don't want to work on newer engines.