Well, I found where the screw goes. It is one of 2 that hold the print head fan onto the print head. I also found a post on another board about the limit switch cables and connectors being an issue So I wiggled the connectors and cables on the affected motor assembly and I am back in business, at least for now. The print head stops at the limit, and beeps and indexes itself properly. Fingers crossed that is it for awhile.