Mystery Furuno proprietary nmea sentence



I'm working through a bug in my system and have come across a sentence I can't find any documentation on.

$PFEC, idfnc, R,4*3c

Is this an error message or what?

Any help would be much appreciated.
It would be extremely helpful if you could provide us with which instruments you observe this sentence.
I'm seeing it through a Brookhouseonline wifi multiplexer on my iPad. The network includes; Furuno GPS chartplotter/radar, Garmin GPS, B&G depth, wind, speed, Furuno AIS receiver, all attached to a SeatalkNG network of Raymarine i70 displays via an Actisense NMEA 0183 to 2000 converter
Yes, that is a Proprietary sentence, but should not have any affect on the network.
What bug are you experiencing?
The i70 instruments at the helm are losing all data after running for a few minutes. There's one more in the nav station that goes down too at the same time. All data quits, but if I unplug the Seatalk cable to the helm the data comes back to the one at the nav station. I thought there might be a sentence conflict and hadn't seen the PFEC sentence before. I thought that might have some info about a conflict.

Everything was working fine after i added them and the actisence converter to the network six months ago and then one day about two weeks ago after I had been anchored for a week (I'm cruising in Fiji) I turned on the network and boom, problem. I've tried isolating each of the helm instruments one at a time, but the same thing happens so I don't think it's an instrument gone bad.
Most manufacturer s use proprietary sentences and if not used by the system, they are ignored. That isn’t your problem. Intermittent problems are the worst.
Thank you. I didn't have detail of what those sentences did, so very useful.

And the good news is I just found the problem. After testing everything one piece at a time, I finally discovered a defective SeaTalk NG connector tee. Replaced that and the system is back running without the hiccups. Yay.