Dreamstation 2 doesn't heat

I obtained my Dreamstation 2 from Kaiser about two years ago. Until a few months ago, I'm not sure exactly when, it would no longer deliver heated air to the heated tube, even at a maximum setting. This made it less comfortable to use, and I no longer used the device as often, though at first I wasn't quite sure that was the reason for the discomfort.

Kaiser's support for such equipment isn't outstanding, at least in my opinion. They offered a warranty exchange but warned me that it would take a while, during which time I would be without a CPAP. I would be willing to get a repair done at my own expense if the cost was reasonable, though I don't know where. (I live in Portland OR.) I could also purchase another unit, not the same kind, but this of course would be the most expensive option.

My SpO2 is about 92% in the absence of much relief from the CPAP, so this isn't a medical emergency. But I'm wondering what course of action I should pursue?

O2 is not the only measure of risk. Apnea can still "get" you.
This is your chance to get off the Respironics merry go round.
Buy a Resmed auto from LSAT, cpap.com, or secondwindcpap.com.
You can always send a bill to Kaiser, along with a letter from an attorney.
You have a right to coverage, regardless of their excuses.

Remove the water tub and carefully feel the heating tray. If it is warm or hot, the humidifier is working. Have you checked the heated hose?

Nice catch.
You have to actually check the heating surface,
also reduction in water level, considering relative humidity in the room.