I am running FreePBX 2.6 with asterisk 1.4 by Elastix 1.5, i have IVR and 4 queues on this box, the PRI connected to CISCO 5500 router, when the caller enter the system it go to queue and listen the MOH, sometimes while he is listening to MOH he sent again to IVR and he start from again, and sometime he sent from position 2 for example to 3 or 4

how can i troubleshoot this case