Parts don't have to be failed to be good candidates for replacement. Roller clutch parts that show wear are liable to hit the can. It's not like they are expensive or unobtainable.

And it's okay to decline work from someone who wants to nickle and dime you on everything. They will be the first to expect it to be fixed for free when it breaks, regardless how they broke it.

If the results don't match the theory, change the theory.