I used to get SNI-PEER alarms from my center-stage switch too. It occurred when there were errors on my T1 that connected the remote PN back to the center-stage cabinet.
If you're connecting your PNs with T1s, then you might want to check the T1s on the DS1 facility card.
The command is test ds1-facility <location>
Remember that there can be as many as 4 DS1s going into a DS1 facility card, so the location is more than port network-carrier-slot. It also ends in a, b, c, or d for the various DS1 spans.
In my case, the specific problem was caused by a mis-configured DS1. Part of the span was setup as ESF/B8ZS, and the rest was was D4/AMI.
Because an ESF/B8ZS circuit introduces bi-polar violations as it's signalling, it would alarm periodically. The PBX can tolerate a FEW alarms, but when traffic got heavy so did the bi-polar violations. Those errors caused lousy audio and, eventually, the PBX would drop and restart the circuit.
Carpe dialem! (Seize the line!)