Why doesn't call transfer always work in Asterisk?

Question

Asterisk

Task:
In the office, you need to set up call forwarding to a mobile phone if the subscriber does not pick up the phone for too long - he went to bypass and so on.

My implementation:

same => n,Dial(SIP/${EXTEN},30)
same => n,Dial(IAX2/rset/8920**********,30,Tt)

Problem:
Redirection does not always work.
For most calls, everything is normal - 30 seconds and the mobile phone starts ringing.
But sometimes - the call comes back.
those. The phone stops ringing, takes a couple of seconds and starts again.

Can anyone suggest which way to dig?
It is better not to offer service codes for translation. the subscriber leaves the workplace often and not for long

Answer 1

This is how I do it, after 30 seconds both phones will start ringing.

[out-call-wait]
exten => _X.,1,Verbose(----Wait-before-Forward-to-mobile---)
 same => n,NoCDR()
 same => n,Wait(30)
 same => n,Dial(SIP/trunk/${EXTEN},120,tT)
 same => n,HangUp()
 
[out-call]
exten => _XXX,1,Noop(----------------Internal-call----------------)
 same => n,Set(EXTEN_MOBILE=380674444444)
 same => n,Dial(SIP/${EXTEN}&Local/${EXTEN_MOBILE}@out-call-wait/n,120,rTt)
 same => n,HangUp()