Help! 612 Seat adjustment

Hi - i have a recurring problem with my seat adjustment on my 612. It inexplicably fails from time to time, the dealer I use seems able to fix it simply but hasn't mentioned how... I've just had this happen so the controls on the drivers side seat don't move the seat at all - and its a lovely sunny weekend... can anyone explain or speculate what might be wrong? loose connection, or fuse, or something at a guess. I've scoured the forums but can't see a similar minor but recurrent fault. Any help much appreciated! thanks, John