I would do as the manufacturer suggests.
On the other hand, my water softener for my house was acting up a while back, I disassembled it and cleaned it and used my pool gasket lube on the gasket and it hasn't given me a problem since - the setup and the way it works is pretty much identical in operation to a pool filter just smaller.
As for glueing the replacement gasket in, try to find out what hte manufacturer suggests, but I would use rubber cement to allow for flexing without tearing the glue or gasket.
Your current gasket could have a deformed portion on it from the way it was packaged/stored and that is what could be causing your problem, outside of that, have you checked for burs and scars on the surface it moves on?