Sorry for dominating the emails, folks. Community Cycles is in all kinds of transition, and we're looking for help.

I don't know all the details right now, so I'll keep this general.

We've been lucky enough to have a volunteer show up who's very motivated and enthusiastic about our mission and our programs. This person has gotten really involved in existing programs and even helped work on and start a new one.
 Recently, this person was asked by another shop visitor a mechanical question, since it was clear that the volunteer was more staff like, and less client. The answer given was very incorrect (one of the details I'm missing is what the quesiton/answer were), but this was witnessed by another very competent experienced mechanic, who was uncomfortable correcting the misstatement in front of the group.
 In another situation, the same volunteer was seen making very basic mistakes when working alone on a bike. From what I understand, the big one was being asked to install cables on a bike, and neglecting to include housing.

We would like to continue having this person as a part of our team, but we also need to make sure the advice and work they do is correct, safe, and appropriate.

One other wrinkle, is that the two incidents were witnessed by two different staff members, both very skilled mechanics.

How to approach the volunteer? Any help or experience you folks have would be greatly appreciated.