Ed,
Yes that helps explain the situation. It seems to me the app_rpt event management system is the wrong approach to this. But I could be wrong. Have you seen this wiki page? Also see this topic for event scripting example.
Is the digital bridge DVswitch and is the connection within DVSwitch? If so I can’t imagine the talkback side of app_rpt sending it’s telemetry to the digital side. But I know nothing about chan_usrp so I’m not going to be any help with that. Perhaps setting duplex=0 with linktolink=yes would help.
Maybe @N4IRS can shed some light on the subject.