Not an hour after that post, I get an email from C2 saying there is a beta version that cures the glitches with an attached .7z file. I verified this morning that it wasn't a bogus email, and loaded it onto the PM5 per their instructions.
First 2 minute test piece (before I disassemble and reassemble the monitor arms yet again) looked good. I now have firmware Version 257, Beta build 7 installed.
Obviously, there are more customers like me out there, just not part of this forum. I apologize for my frustration-induced previous post.