[Motorola] MSR-2000 Repeater Squelch Tail?

[Coote, Jay]

I have inherited a few MSR2000 repeaters.
 
One has a repeater squelch problem.  When a subscriber drops carrier and
PL, there is an annoying squelch tail heard over the repeater.  If the
user drops PL first, or is reverse burst, no squelch tail is heard over
the repeater.  
Another MSR2000 (looks like the same model) does not have this problem
and sounds great.
 
I tried exchanging all boards except motherboard, receiver and exciter.
 
Anyone have a clue?
 
Thanks