Thanks for the heads-up on the SoClean warranty exclusion. Good to know. I checked the ResMed online information and it appears the SoClean warranty exception/exclusion (am I saying that right?) only applies on machines sold after February 2020. I got my current machine in early July 2016 (it was a warranty replacement because of failed memory card socket) and its warranty has expired anyway -- it was originally less than 5 years if I remember right. I've pretty much stopped using the SoClean unit as I can't see that it does much of anything -- except possibly harm the CPAP machine as you mentioned and instill an unpleasant odor in the system for a few hours.
I also found something in ResMed documentation saying the CPAP's motor was affected (more 'motor noise'). It didn't mention anything about the 'thumps' I am starting the hear which don't sound like motor noises. I've had no 'motor noise' increase that I can tell. But then my hearing is lousy so I might not hear a change. My wife would, however, but she has said nothing about it.
Thank you again as I might get a new machine soon after my 5 year anniversary and I don't want to do anything (such as use my SoClean system) to void its warranty.
Tubaman / Carl