I'd post the question over ARF.com in the armory section under silencers sub forum and ping @Mageever. Pretty sure he'll show up and comment as he posts regularly over there.
I have the old collars and it's great to see Dead Air is improving their products. I love my Nomad and Sandman.
Finally got a moment to replace the compression nut and compare old vs. new.
Dead Air was right in their presumption that the compression nut was out-of-spec, causing difficult installation/removal of my Sandman.
First pic is of the original compression nut. The alignment notch is off-center from the tooth below it. To install/remove, I was having to go to full unlock and then 1 click in the lock direction.
Second pic is of the new compression nut. The alignment notch is centered with the tooth below it. I can now go to full unlock and it installs/removes perfectly.
TL;DR - If the alignment notch isn't centered to the tooth below it on your Sandman compression nut and you have difficulty installing or removing suppressor, the compression nut is out-of-spec (unless you're running a non-Dead Air muzzle device, that experiment is in your hands...). Replacing the compression nut worked like a charm.