[TenTec] Orion drops lock?

[Martin Ewing]

My 565AT is developing an unpleasant operating mode, where the main Rx
output stops. This is on 40 CW, for example, but probably on other
modes/bands also. If I fiddle with the VFO, I can bring it alive seemingly,
for a time.  I hear CW signals, but changing the VFO setting does NOT tune
the Rx.  I have no idea what freq. is actually being received!   In this
mode, there is no Tx output, either.   It doesn't matter whether VFO A or B
is selected.  The sub Rx works normally.
I have tried power cycling, master reset, and battery reset.  None of these
cures the problem.  If I power off for an hour or so, the radio comes up
normally.  The radio is happy to run for many hours until it flips into this
non-operating mode -- it does not appear to be triggered by operating
temperature alone, but some random operating event or condition that I
haven't been able to narrow down.

Without digging into the radio, I have the sense that there's probably a
phase lock loop that has drifted close to the edge of its operating range.
 It ought to be a simple thing to adjust (he says).

Has anyone else seen this problem?  Is there a field adjustment procedure?
 Or is it time to ship it back to TT?

Thanks for your advice!

73 Martin AA6E