I've some ATA186s on remotes site that became unregistered (congestion tone) from CCM cluster 6.1(2) of 2 servers. There is always connectivity between the cluster and the ATAs. If it that was the issue they became registered on local SRST gateway, and there is no logging of the ATAs trying to do that.
I've tried shutting down and up the interface on switch where are connected the ATAs with no success.
The only workaround is to remove power supply from ATA and then reconnect, then the ATA register with the cluster.
The ATAs has firmware ATA030203SCCP051201A
The ATAs are from 2005, so maybe there is a firmware issue.
Any help will be appreciated.