I have never had or used any machine that skips anywhere, and have never noticed the A on any machine being prone to it.  Can't find a way to believe that any such problem has anything at all to do with the mechanism - how could that even be possible? - all manufacturers conspiring to make this the universal 'devil-key'?  I think not.
Try a miniature dumb-bell that just fits on the tip of left little finger - raise and lower it one hundred times every day.