Hey Scott,
Incoming LOF indicates that the PRI is dropping frames. How this should be setup based on the information you provided is the PRI Circuit should be split into two separate cables. One cable goes to your pbx and the other should go into the port on the back of the recording platform. I'm going to assume this is an Oaisys call recorder? That was discontinued not to long ago.
If you are losing frames on the one cable but the call is fine at the pbx I would say it could be a bad splitter, bad cable from the splitter, or a faulty PRI interface on the recording server. The server should have LED Indicators for the PRI cable, Do those remain lit while the call is dropped? I have had issues with Oaisys' PRI Interface cards in the past just shutting off. But they generally tend to stay off completely
Thanks,
Travis