Squelch problem on BPR40s

[KI4LTX]

I was just wondering if anyone else has seen this problem. I maintain several systems that use BPR40s. I have lately had quite a few come back with the problem that the noise squelch stays open on narrowband frequencies (green busy light all the time). The squelch is fine on channels that are programmed for wideband. A squelch alignment did not resolve the issue, so I sent a few to the depot. Every one of them came back with the statement:
ALIGNMENT-ADJUSTMENT

COMPLETE PM- FCC CHECK
ALIGNED-TESTED TO SPECS.
BOARD/UNIT REPLACED
FREQ SET DEFAULT/TEST
RADIO MUST BE PROGRAMMED

I have received several more in the mean time, with the same symptoms, from two different sites. Any thoughts?

John