Zap channels won't hangup when transferred

Hi all!

I’ve just updated my freepbx with all tha latest modules and upon testing some functionalities some of them are having trouble already. I’m using asterisk 1.2.35, the latest zaptel, and the lastest core&framework or freepbx. has anyone else experienced this, when i try to call out on pstn using my ip phone and transfer the call to the conference number we’re using, after all has hung up, the call to pstn is still connected on the conference room, even if i hangup already the pstn phone. upon picking it up after 10 seconds it’s still connected. i checked on the asterisk cli using show channels and it’s still connected. even amportal restart won’t disconnect it. the only way to disconnect it to restart asterisk itself. when I dial the other way, meaning call coming from pstn going to my zap channel to my ip phone, calls are good and tranfers and hangups are all good. it’s just the outbound where i’m having trouble now. here’s the scenario:
TROUBLE:
IP PHONE -> PSTN
IP PHONE transfers PSTN to CONFERENCE 6001
IP PHONE joins CONFERENCE 6001
IP PHONE hangs up, PSTN hangs up
upon checking show channels in asterisk cli, PSTN still connected
upon picking up PSTN phone after 10secs, it indeed is still connected
GOOD:
PSTN -> ZAP->IP PHONE
IP PHONE transfers PSTN call to CONFERENCE 6001
IP PHONE joins CONFERENCE 6001
BOTH hang up and upon checking show channels all are already in hung up state
all are hangup properly.

Hope somebody could help me resolve my issue. TIA! God Bless