Openvox GW1600 + VS-GWM400W call hung up busy detection

GSM gateway (in WCDMA only mode) connected by IAX2 trunk to FreePBX 14.0.3.17.

When:
1. Call to GSM phone and it's busy - all ok, Asterisk detects busy signal;
2. Call to GSM phone and accept call then hang up - all ok, Asterisk detects busy signal;
3. Call to GSM phone and do not accept call, just hang up it - Asterisk does not detect busy signal, and Asterisk go make call to another trunk of GSM gateway and so again and again unlimited times. In logs have this message:
Dial failed for some reason with DIALSTATUS = CHANUNAVAIL and HANGUPCAUSE = 66

Any suggestions about this?

Hi sir,
please add my skype john.sun live:e172816a6bbf5220
I will help you check.