@Andymat You mentioned the button not working enough to make me curious what kind it is. Those would work much like a computer keyboard key, wouldn't they? Just wondering if maybe a spider may have crawled in and died so that canned air might work/help.
There are three rocker buttons on the right of the machine +/-. The first does the stitch width setting, the next the length of the stitch and the last one is to adjust the skew of the wider more fancy embroidery stitches. This works to increase the skew but does nothing when you try to reduce it. So to get back to even, you have to change the stitch program and then go back to it.
When you press any of the rocker switches, there is a definite feel that you have pressed it, like, as you say, a keyboard. I do know from a you tube video that the buttons are pressing onto switches on a printed circuit board inside the machine. I just think one of the switches is just not making the contact properly but to find it , I will have to take out the board. Probably not too much of an issue. As you say, it might be just dust or fluff but at the moment it is not that much of a deal. So I will prob wait till it becomes more of an issue. Or I might get some advice from a dealer. We will see.
Thanks for your thoughts.