I need to apologize - I just rechecked the laptop and it is fine. Not certain why I thought the problem was duplicated there, but it is not - it's only on the desktop. Also, JUST AS A TEST I installed Directory Opus on another desktop system running W10 and upgraded that system to Threshold - and there were NO problems (I then ununstalled the app so as not to violate the EULA).
It seems the issue is isolated to the one desktop. It is virtually a clone of the 2nd desktop I just tested (same startup items, AV, new high-powered systems, etc). I'm fairly technical (on staff at multiple Windows support sites) and am stumped.