The Radio Information Board

I have a vertex 9000 repeater in commercial that keeps losing sensitivity on the RX. The antenna is new, the coax is new and everything works fine with a Kenwood repeater installed. Both times the RX will not open until an input of 5 micro-volts, not .5. The Kenwood will open at .2. I sent it back under warranty, installed it and about 6 months later the same problem. In other vertex radios I have worked on the failure is in the ceramic filters. Vertex must have gotten a boat load of bad ones. Is anyone having filter problems with the 9000?
Kruser