Check the NCOS of the trunks between the PBX and FAX server. Also, make sure that the starting arrangement (IMM IMM, WNK WNK) is the same for both the server and the PBX. As stated above, make sure your server is pre-pending the outgoing digits with your BARS access code (AC1, usually 9.)
I have a few RightFAX servers attached to 81s and 61s and they've never had an outbound issue. Inbound, however, is a different story.
Seems like once per week-- as pbxn has also experienced-- they need to have their FAX service stopped and restarted in windows. The issue seems to be with the starting of the trunk calls. After some time/traffic has elapsed, I'll get channels (different ones each episode) in LCKO. Tracing has shown that the PBX doesn't outpulse the digits to the FAX server because it never receives the wink back at the start of the seizure. Again, the server folks just have to stop and restart a service in windows and the problem goes away for about a week. Hardware or software buffer issue on the FAX server?
--T1PSTN