Excessive # of RabSystemRelease drops

what could be the reasons for excessive # of RabSystemRelease drops (Ericsson 1900 Node B).Site has dedicated antenna and coax lines and no VSWR or TMAs issues.No hardware alarms.The problem is only in one sector.Tried connecting another sector hardware (from C sector) to the problematic sector B antenna system then problem is gone but any possibility of the cable swap etc has been checked from top to bottom.Once swap the sector C RabSystem Release no. are still fine but if we put it back the normal way then problem starts only on that sector (which is sector B).Changed the PSC (scrambling code) just to see but no different.

The software on the hardware is the same with other node B’s. what could be the issue?

Apprciate your input and time.

Thanks
SB