If it's a collective group you can use twinning in place of forward but watch the number of channels if you have it on mor than a single user.
If that's not the issue, is it a SIP connection? If so check the SIP trace. the IPO (depending on version) can do in my opinion stupid stuff with hunt group twinned calls. e.g can put the group ext number in the from field.
Hmmm Actually, I note the subject says it PRI. So no SIP trace to check, My feedback probably no help at all.