I have multiple locations serviced by CCM 4.1(3)sr3a.
Occasionally, a site's FXS ports will unregister. I will need to reset the gateway, and also do a shut / no shut on the ports to bring them back up.
When this happens, the PRI at the site does NOT unregister. Also, it is happening at multiple sites on multiple IOS loads. When it occurs at one site, other sites are not affected at that time.