This morning I got this 33-R message on the LEN that has the CPU-1 PHI programmed on it. It's a MINOR alarm in the system, the red alarm light is on, and ADTF shows Side 1 (the backup side) not mounted, for both LAN 1 and LAN 2.

All phones and services are working fine, and it looks like the backup side is gone.

I never had this before. I checked the error message and the codes relating to it in the Operations and Maintenance manual, and the description says:
"Failed to communicate between the telephony server and the IP terminals. Note: The system automatically resets the appropriate terminal for the recovery purpose".

And the manual's recommended action:
"This message is output when the connection can not establish between the Telephony Server and IP terminals. The cause could be considered that related equipment are abnormal. Make sure that the MG with the MAC address shown on the message is available to use. If it is listed as available, keep watching it. Otherwise, contact NEC engineers."

I also checked what the LEN number for the equipment is in the error message and found that it is the PHI for CPU 1. I then ran a LLEN report for the system and found the following oddity. There are stations programmed right in the middle of the PHE, which should take up 2 groups and no stations should be programmed on those LENS that the PHE is occupying. While this is definitely wrong, the system has been running like this with no problem for over 2 years.

So having no other ideas, I'm reprogramming those stations away from the PHE and PHI-s.

Any further recommendation? Like how do I even attempt to restart side 1?

This is resolved. I had a bad CPU board which got replaced. All systems are normal now.