W52Ps continue ringing after call picked up on other phone

[Bobcat19]

Hi guys, bit of a strange issue here. We've got 5 T28Ps and 3 W52Ps (on one base station) all set to ring on an incoming call, and normally this works fine. However today something strange happened. When a call came in, all phones rang as per usual, except when the call was answered on one of the T28Ps, the W52Ps continued to ring, and ring and ring until the cancel button was pressed on both of them.

Has anyone encountered this problem?

This happened all day until I reset the base station but I did get a pcap from the base station of the problem occurring, if someone could examine it and tell me whats going on that would be great. Let me know and I can send you the pcap.