My EX21 broke about two months after the purchase. It turned out to be bolt in the upper arm that had been tightened too far. Ray @ Seyco said there was a batch of these that had gotten by QC at the manufacturer. Ray simply replaced my machine instead of repairing it. This was in March of 2012, so, if you purchased it during that period, this could be your problem.
Tony,aka, Toneman