Ringing in background

We have a end user with a polycomm desktop phone and sometimes (it appears to be random) when they answer the phone they will hear a ringing (the ringing you hear when you call someone) in the back ground. I thought it may have been the phone but swapping it out did not fix the issue.

The Setup

The Phone has two extension configured on it (one for each outbound number they call from)

When phone calls come in they pass through a Time condition then to a ring group (ringall and everything else is default).
There are three extensions that are part of that ring group.
Only one extension from each phone is part of the ring group.

The other two users that are part of that ring group have not noticed the issue.

If you have FXO ports (anaolog lines), check the wiring for “split pairs”

Thanks, everything is pure SIP int his setup.