Years ago I took a class and offered at a lqs, I was the only one with a kenmore and every time I had a question or problem it was 'because I had a kenmore'. I even heard the owner / teacher whispering to someone else about 'the kenmore'. The class turned me off free motion work because it just wasn't going to be possible to do this on my machine.
Fast forward a while, now I have a janome and bernina. I take the smaller bernina toclasses. I was having a problem in a class at my new lqs, and I have taken several there without trouble. But this time something was going wrong for me, and the owner and another student were saying, Oh it's just the way bernina is.....
So now I know that the least reliable part of a machine is the loose screw operating it.