Michael Thanks for suggestions, will give them a try. My temporary workaround for FT8 only:
- Uninstall Omnirig
- Change wsjt Radio settings back to 7610
- Not use any "Rig" connects to Log4OM to avoid port conflicts.
- Retain background Log4OM<>wsjt connect so auto-logging still works

An unrelated issue- seems like the 2nd virtual port associated with the 7610 doesn't work, either with Log4OM or wsjt, although it's viable according to the PC device mgr... hmmm...