I've got a CIX 670 with five cabinets (3 main, 2 remote) with a RRCU card connecting them over fiber. It's a high school (remote) and technology center (main) campus.

Recently we've been having strange issues at the remote site. The phones (DKT phones) are powering off and on very briefly and coming back up. Kind of like if you were to unplug the cable in the back and replug in quickly you'd hear the speakerphone pop.

This happens in random intervals of 5 seconds to 5 minutes, sometimes more. I've tested a call with an external number for 10 minutes and it happend at least twice where the station goes off for about 1/2 a second and comes back up and the call is still on! This does not happen at the main site at all. I checked stations on the same cabinet the RRCU is on over there too. The sites have worked great for years, this is a recent thing lately but it happened before like 10 months ago and switching the power supply from EXT to BASE on the 2nd expansion cabinet at the remote site seemed to keep it at bay.

To debug this just this weekend we've switched all the cards between the remote cabinets to rule out the cabinet, switched the power supplies between those two cabinets, and power cycled everything at both sites several times. I even bypassed the surge protector thinking the cabinets were going down. I haven't noticed the power supply lights flashing if it were a power issue either.

Any advice out there for us? I'm leaning towards replacing the remote RRCU (the slave one I guess) but maybe replacing both is in order?

Thanks in advance to anyone who can help!