Strange Group problem

I have a Asterisk based system (IPitomy actually). This system has a Digium CO card installed. so all the lines are loop start. We have a call that rings into a Menu then the called uses a single digit to route themselves to a Group of phones. The group consists of 3 phones. The Ring strategy is set to Ring ALL. Every once in awhile a call comes in and it appears that the strategy has been changed. One phone will ring, then another and then another. The worst part of this issue is that the users cannot answer the call. The failover is to another group that has different phones. The agent ring time is set to 23 seconds and the Timeout set to 24 seconds. I was told by IPitomy Tech support to keep the two timers different. Anyone have any ideas what might be happening here?

Thanks for any help