Calls cut out after a few minutes

Hello Guys,
vd version is 2.2 rc5
asterisk version is 1.2.30.4
using ztdummy
when a call is transferred to a 3rd party number by an agent the 3rd party and the transferred call party get cut off after a few minutes, they only hear a long beep and after that the call gets hung up
vd version is 2.2 rc5
asterisk version is 1.2.30.4
using ztdummy
when a call is transferred to a 3rd party number by an agent the 3rd party and the transferred call party get cut off after a few minutes, they only hear a long beep and after that the call gets hung up