Did you drop any of the housings at some point? Could have developed a hairline fracture leading to bypass at the seal. The seals themselves can be damaged but unless your really Mishandling them and tossing them around they should be fine.If you want to go with best practice I would, especially with blowing through RO membranes since that isn't normal.
However it could still be a bad seal or just the temperature your running the unit at.