My installer called me today. He had talked to Aspen (they called him to give him up update as they knew mine was going in) and got the same explanation. They found that the 30 foot (I think 30?) cable that is shipped for the RSM was having noise issues at about 25 feet in length. The RSM issues they had found, was where the installer didn't trim the excess cable off, and made a big-ass service loop with whatever was remaining. My cabling was only about 14 total including the service loop he left, which is why we didn't see any issues with the RSM.
I imagine this was a tricky ghost to find for Aspen. Their test benches were probably already wired up with a short length of cabling so they'd never see the issue even with the returned units.
I go Monday to sit in the airplane and sign-off on all the work he's done, before the installer puts the interior back together. I had a crap ton of other work done while he was doing the E5, wired in some front and rear seat audio inputs so my 3 year old can listen to her iPad and ABC Mouse game without disturbing us, or ATC disturbing her. hah. He also had to fix a bunch of pitot-static plumbing hack-jobs that'd been done over the 40+ years of its life. I have no idea how it didn't leak like a sieve. Hopefully if Monday's sign-off goes good, I'll be flying it home Next Friday to play with the Aspen.