Transfer calls between SIP trunks fail

Thank you in advance for your assistance.

I have two SIP trunks

Trunk 1 is SIPSTATION

Trunk 2 is an SIP device connected to PSTN (SPA-3102)

A call comes in on trunk 2 then you transfer the call it will go out through trunk 1, when you complete the transfer the caller on trunk 2 is disconnected.

You can conference between both trunks and all parties can hear each other but as soon as the phone hangs up it drops all callers, same with transfer - everyone can hear but once the extension hangs up all the callers are hung up on.
This only happens with these trunks.

Any ideas why I cant transfer between the two trunks?

Thanks!!!

Freepbx 2.9.0.7

Trunk 2
username=2-XXXXXXX
type=friend
secret=XXXXXXXX
qualify=yes
port=5061
nat=never
incominglimit=1
host=192.168.1.115
dtmfmode=rfc2833
disallow=all
context=from-pstn-e164-us
canreinvite=no
allow=ulaw&g729

Trunk 1

context=from-pstn-e164-us
type=peer
insecure=very
qualify=yes
sendrpid=yes
trustrpid=yes
dtmfmode=rfc2833
username=XXXXXXXX
secret=XXXXXXX
host=trunk1.phonebooth.net
disallow=all
allow=ulaw&g729