How to find the reason why our asterisk is not transferring the sip call to the provider?

Question

Asterisk

I heard a complaint from users that when they make an outgoing call, they hear silence and then reset! I went into the database and saw that these calls have lastapp = Busy , lastdata = 20 and there was no call at all according to the billing of the VIP provider, although our database says that the call went through this provider. Made a selection, it turns out that every 20th call leaves ~ 5%. It turns out that our telephony itself resets the call.
How can you track down the problem? And how to solve it?

Answer 1

Busy(20) is called
to make it audible

same => n,Answer(0.5)
same => n,Busy(20)
same => n,Hangup()

another unanswered option

same => n,Playtones(busy)
same => n,Busy(20)
same => n,Hangup()

and that's why you need to look at it in verbose logs

Answer 2

Log * look with Verbosity 3+ - there is probably an answer to your question