I've had to switch a few clients to the alternate voipo data center to resolve registrations dropping for no reason.

Only need to move a small percentage of clients, and it does seem to resolve the registration issues.

No solid pattern, but seems to affect a small segment of cable internet users, mostly Comcast business class or Time Warner business class. Maybe there's something different about those networks?

We don't have the problem with other voip services that we have at the same locations as backup.