question

Polycom VVX-500 goes haywire with multiple incoming calls. We don't use auto attendant so every call gets answered by a human. Today we had a situation where the phones were ringing but nobody could answer. After looking at our call log, 3 calls came in at once and another call went direct to a separate group. Has anybody else experienced this? The call log even showed that 2 people answered a phone call which isn't at all possible. Does anyone have any idea how this could happen? Anyone familiar with this situation?