transfer call to cisco spark app, call drop auto 20 sec.

[peraocompany]

Hello, I have problem with 20 sec call drop auto call transfer to cisco Spark client.

I have topology  SIP operator ---> SIP trunk ---> cisco CME + ip Phone  ---> SIP trunk ---> Cisco Spark APP.

Then I recieve call from SIP operator all is ok. (call have both audio and can more 20 sec work).

Then I do transfer to Cisco Spark all is normal call is perfect (audio is both), but only 20 secm then I recieve from SIP provider Disconnect Q.850;cause=31.

Then I do call from CME IP phone to Cisco Spark APP I have no problem with time limit.

Thank you in advance.

[peraocompany]

I have update. I try use Cisco Spark for Windows, and I have no any problem this 20 sec call limitation. I try lte, wifi, Ethernert, all time call have not limitation. Then I try use latest iPhone App, and  Android app, call drops auto 20 sec both (lte and WiFi).