Many thanks for the “executive summary”, Bryan 
That confirms reports by others I’ve seen on problems encountered when attempting to share databases amongst multiple devices.
So, conclusion for @riverman; you could run multiple devices against the same set of images - BUT, you would need to delete the database before each invocation of PL - and use sidecar/.dop files to retain your correction details … (This is my approach, even tho I don’t use multiple devices.)
The downside is that you would lose ability to retain keywords - and you cannot define Projects … as these details are not held in sidecar/.dop files.
John M