The short answer to this is that there isn't one... the problem vanished without explanation.
I contacted our VAR. We stepped through a number of iterations with them asking for certain information and requesting a handful of temporary coding lines to help understand. I could fail the macro repeatably and predictably. After several rounds of this they finally elevated this issue to SolidWorks.
With time constraints and work needs I shelved the macro for a few weeks until SW could weigh in. They set up a GoToMeeting session to observe the macro in action on my machine. ...And it worked without issue. Did not fail. At all. And hasn't since...
What changed in the interim? Certainly nothing in the code. My workstation had been rebooted a few times - and, yes, I had rebooted it a few times while trying to diagnose the macro. Some Windows Updates were deployed in our office. The ancient antiquated under-powered office PC that hosts the PDMWorkgroup vault in the background while also acting as a full-time desktop was also rebooted with the Windows Updates install. (A proper server to run PDM so that we can unload it from the desktop as well as upgrade the software has been a stated TOP PRIORITY for three years running now... not holding my breath). The Perseid Meteor Showers are in action. Beyond that, I've got nothing.