SX200ICP MX S/W 5.0.0.18 installed about six weeks ago. 132 analog stations 6 IP sets 1 IP Console 1 PRI and 2 LS Trunks. The problem is with the PRI. On 5% of the inbound calls the console can hear the inbound caller but the caller continues to hear ring back and never hears the answering party. When first installed we had a couple of complaints but now is up to about 8 or 10 a day. SMDR shows the call as answered and the carrier says the PRI dump all looks normal as if the call has been answered. Any Suggestions?