T28P Phone identifies itself by IP address instead of user and extension

[mazuno13]

Intermittently, internal calls from some phones show up as coming from the phone's IP address instead of the user and extension. When this happens that phone cannot put calls in park, the call quality is worse and their calls are logged by the phone's IP address instead of username and extension in the log (Barracuda 370) while the issue is happening.

I've compared phone settings and firmware and everything is the same. The issue has remained through a few firmware updates. Always intermittent and has not really gotten any worse or better over time.
Obviously, rebooting the phone fixes the problem temporarily.

Thanks!