" Incidentally, regarding the carbon monoxide alarm, I’ve had to wonder whether it was actually broken or was just responding to a dying battery (it lights up green, but I’ve actually tested it using the tester button, and it doesn’t work - but it’s no longer broken in the sense of intermittently beeping)."
To me that statement makes me think you tested it and it didn't work. It should sound out loud if it is working. Pull it out and look at the back where it will have manufacturing date and lifespan. Molded into the front or on a label on the back it will have a reference to the flashing codes it can use.have you tested for 12 volts at any of the affected items? The stove typically requires no 12 volt power so it will work as long as it has propane. Keep in mind that a 23 year old unit could have lots of issues no matter how good it looks. Brand new high end units have flaws!
Might be time to go over the entire unit checking connections. A pristine unit may have had very little use which can be worse for some systems than heavy use.
