My rear break failed about a month a go, and I had to lay down the bike to avoid an end over. Just got it back from the shop road it the 45 miles home and took it out today and it happened again. It works fine and then it just fails, almost like sever brake fade. Fluid levels are fine, and I can't find a leak. Could it be a bad gasket in the master cylinder itself? The dealer, Worth HD in KC, seams stumped. Funny considering the bikes are built her. Any suggestions?