You know, I was a technician for 38 years, and I would walk in the door and whatever was called in would disappear. That being said, a good tech knows these things can be intermittent, so I would from past experience check out the usual problem areas hoping to find the culprit. However in the Automotive shops they work on job/rate hours. I too was rated by the time for repairs, but a long time ago I decided that the little extra time prevented call backs (repeat problem call). It paid off, as my customers knew that I gave it 150% and didn't try to bullXXXX them when not doing anything. My equipment ran longer between calls, and the uptime for the customer gave them more productivity, a plus for not only them, but also for my company because they didn't have to eat more time and expense on the repairs. Sorry for the long explanation, but basically there are those that have pride in their work, and want to make customers happy, and those that think their half jobs will get the customer out the door. Its hit or miss, but I would take it back for a call back, and maybe you will get a different tech, that knows what the fix is.