I was having the same problems with random disconnects.
The firmware on there doesn't like certain line conditions/errors and was throwing it's toys out of the pram.
I had to swap out to an old WAG160n that I had laying around and used that to diagnose the line problems.
I had an issue where even though PN had requested BTOR fix my downlink SNR to 6dB, the router would initially set itself to 6.9dB or thereabouts for about 60secs and then shoot down to 1dB. Line would then go up/down like a yo-yo.
I don't think PN will be using that router for too much longer.
Firmware has so much disabled, it's next to useless...