B-15R - Do they all buzz and rattle at high volume?

Merryweather Stone Firm

I recently bought a used B-15R. It sounds terrific with the gain at 10:00 and the master at 12:00. However, it starts to buzz and rattle at 12:00/12:00, and at 3:00/3:00 it positively turns into a chainsaw. Of course, I always remove it from the dolly before I play it. Further, I always make sure that the top is latched on nice and tight. Still, at performance volume, the fliptop and cabinet rattle against each other with such ferocity that the amp becomes unplayable. Is rattling/buzzing common with B-15R's? The top gasket is intact and still fairly plyable. Does anyone out there have a B-15 that they can crank up without a deafening buzz coming from the top of the cabinet? Is there anything I can do to lessen the rattle? New gasket material perhaps? Thanks.