Do you offset the seal so it doesn't line up with the split between the block and retainer ?
I would try this. DON'T glue the seal in the block, nor in the cap. Only glue bottom and sides of seal retainer. Seal joints 90* from retainer surface. Never had one leak done this way. And of course I HATE to ask an obvious question.....but you are turning the lip on the seal the right way?