Just wondering if some of you had the same experience. You are happily practising a piece, several times a day, and suddenly there is this one bar, which never gave a problem so far, turning into a stumbling block without any apparent reason (nothing changed in the fingering, execution or speed, nothing at all). I've had this on a couple of occasions, and it puzzles me why it should happen. Seems like regress instead of progress. Does this ring any bells or is it just me going senile ?