I'm am not very hot on diagnosing sip issues but the first thing I saw was 401 error.unauthorised
Usually caused by Authentication name or password in SIP Credentials is incorrect.
Is the trunk showing as registered in SSA at the time off the error.
Could be the trunk is dropped and the system is waiting on registration to give you a line back.
Is the issue from 1 user or all users.
If you are using internal data then make sure all the users have a correct sip ID programmed in the user sip tab.
13:05:35 3721105876mS Sip: Find End Point2 ac1e14440001c347 17.115527.0 2088 SIPTrunk Endpoint (f17c7c5c) Sip CallId 7363229bc0d39fbadc4366f335f83cd2
13:05:35 3721105876mS SIP Call Rx: 17
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 10.1.10.20:5060;rport=5060;branch=z9hG4bKcec6fe1e252af5c68c4554db51fd7764;received=10.1.10.20
From: "Unknown" <sip:5862262080@10.1.10.150>;tag=5e524f4ef4d65f07
To: <sip:15864885440@10.1.10.150>
Call-ID: 7363229bc0d39fbadc4366f335f83cd2
CSeq: 1160803430 INVITE
Digest realm="fe-4a2b-6w.coredial.com", nonce="1b049a8b", algorithm=MD5
Content-Length: 0
13:05:35 3721105876mS Sip: ac1e14440001c347 17.115527.0 2088 SIPTrunk Endpoint(f17c63b0) Ignoring Q.850 Reason dialog f17c63b0, method INVITE, CodeNum 401 in state SIPDialog::INV_PROV_RESP_RCVD(5)
13:05:35 3721105876mS Sip: ac1e14440001c347 17.115527.0 2088 SIPTrunk Endpoint(f17c63b0) Process SIP response dialog f17c63b0, method INVITE, CodeNum 401 in state SIPDialog::INV_PROV_RESP_RCVD(5)
13:05:35 3721105877mS Sip: ac1e14440001c347 17.115527.0 2088 SIPTrunk Endpoint(f17c63b0) SIP-EP: Decoding of 401 (challenge) RESPONSE
13:05:35 3721105877mS Sip: ac1e14440001c347 17.115527.0 2088 SIPTrunk Endpoint(f17c63b0) UpdateSIPCallState SIPDialog::INV_PROV_RESP_RCVD(5) -> SIPDialog::INV_FINAL_RESP_RCVD(17)
13:05:35 3721105878mS Sip: ac1e14440001c347 17.115527.0 2088 SIPTrunk Endpoint(f17c63b0) ACK SENT TO 10.1.10.150 5060