Its an ios based mtp, so please do a 'show sccp' on the gateway where this mtp is configured. Try bouncing sccp by doing 'no sccp / sccp' if this is the only media resouces configured on the router as this can make the calls drop if there are transcoders or conference bridges configured on same gateway. For an RCA you will need to capture the 'debug sccp packets' from the gateway.
IP Voice Media Streaming Application is running, I restarted the service on several occasions and it solves the problem, however, we will have the problem again. The MTP is deregistered.
In that case the detailed IPVMSA traces would be needed from that subscriber for an RCA. But as you are running cucm 6.1.3 so the best bet is to upgrade to at least the latest version of 6.1.5 available on cisco.com as it does not involve any cost. If the issue persists then traces can be analyzed by someone on forum or you can open a case with TAC. AFAIK 6.1.3 won't be supported by TAC.
