I have no faith in my Janome repair person either. I think it is like the car mechanic that doesn't believe when women come in with their cars. I took it in once for the losing the take up thread thing and he had every excuse in the book as to why it was doing that. Every excuse except that the machine has issues (which I find out later it does).
As for the mechanic I had a Suburban once that would just cut off while going down the road at 50. Lose all power and breaks and everything. Over and over they could find nothing wrong. Nor could they get it to do it. So eventually they replaced the electronic ignition $600.00. When I went to pick it up the mechanic went to bring me the car. He turned the wheel to pull into the parking lot and it cut off on him and he almost took out three new cars on the lot. His face went white. He was only going 10-15 at the time. I said to him how would he like to have that happen going 50? It was a loose wire. I got my $600.00 back. They believe me now.