Airsense 10 making loud cracking noise

I am not new to the CPAP world, and have had two Philips Respironics machines (used for about 5 years each), followed by one ResMed Airsense 10 Elite (5 years) and now an almost brand new Airsense 10 Autoset. Both the Airsense machines have from time to time made a loud cracking noise (like a firecracker going off, or the machine falling on a hard floor - except that it never has). I'm mystified. It's not my imagination, it's not electrical (I use two different power supplies, one at home and one when traveling, both are undamaged), and as far as I can tell it's not related to the forced oscillation that the machine sometimes uses (sequential bursts of air that I was never warned to expect, and had to research). I wondered if the noise was something to do with the humidifier tank seal, or inlet or outlet, but that doesn't seem to be the cause either. Has anyone experienced this noise?

Could it be rainout? Water condensing in the hose and then making a popping/crackling sound.
https://www.youtube.com/watch?v=ctw73sdPU6k