[c-nsp] PPP encapsulation triggering LOF on DS3?

[Kevin Graham]

Just ran into a problem that I'm absolutely clueless on that I was
hoping someone could share some insight..

On a clear-channel DS3 terminating directly onto Cisco DS3 interfaces
on both ends (PA-T3 on a 7200 and some GSR LC on the other) w/ PPP
encapsulation link that had been good for several months went down.
Interface would bounce down and then back up every 20s or so with an
rxLOF, though line proto would never go up with a pile of CRC's on the
7200 side (GSR side was always up/down with no errors). clockrate was
osillating some though always in the 44M range.

Loopbacks either way all came back clean and telco PM also looked
good. However, whenever the link was normalized, the troublesome
behavior would come back. After a round of loopbacks (of course using
HDLC), both ends noticed that the link was running perfectly. Going
back to PPP would cause the same problems..Went ahead and left it at
HDLC and has been running fine.

So... Is anyone aware of WTF could be going on that would cause PPP
encapsulation to trigger a consistent LOF condition whereas HDLC does
not? The only thing that comes to mind at all is perhaps scrambling
(which is disabled), though as mentioned the line has been stable for
months....

Thanks.