I have raced with this cylinder and its a great thing.
I have had it let go in the bearing as well. it was to narrow a bearing and it was moving on the gudgeon ( sideways)
The bearing sizes should be a std size and the pistons made to accommodate that but they dont
S6 wide bearings don't fit anymore, pistons were changed already over a year ago.
If you have some dusty old kits it does fit.
Newer kits also have HUGE bevels on all ports, about 1mm wide. Looks rediculous but I'm sure al 16 year olds like it.