vicidial.org

You're software is sending the wrong ID when trying to BYE to call. It seems to be sporadic. This is the response in the SIP trace "481 Call/Transaction does not exist"

Our carrier is saying this for calls that are not being terminated for many hours. What could be the reason?

Does anyone have any clue on why vicidial is sending 481 signal to our carrier?

Anyone able to help on why vicidial would send 481 on ending the call?

Can't say I've heard of that issue, although I'm not really the SIP expert at the office, so I don't deal with carriers on a daily basis.

Anyone else on why Vicidial would send 481 signal on bye

It is probably an issue when your vici server already ended the call first or your vici thinks it ended the call by sending the BYE to the carrier. However, the call is still active on the carrier side. Let's just say your BYE got lost somewhere internet/network.
After some hours the call is ended by the carrier because they have a maximum allowed call length. So now they send your vici a BYE from the carrier. But since your vici no longer has the call active it sends 481.

This is called runaway calls and it happens from time to time. By the time to time, I mean few times out of 5 or so million calls.

You need to have a capture/sip log of the call to see where your vici sent the BYE. If you sent it properly to the carrier you should have received a response from the carrier in the same log.
Typically those runaway calls should be credited back to the customer by the carrier because it's obvious that those are not real calls and there was no one connected on the callee or caller side.