Thanks, Boilerman. We keep those tube openings clean. Haven't checked the elbow since startup this fall, so I'll look at that. Haven't messed with the thermocouple, didn't realize it was prone to moving, so I'll do that next cleanup.
Good idea on the solenoid, but I'll do that as a controlled experiment, when I can change only that and see if there's an effect over the next 48 hours running.
Cleaned it today, and a bit more charcoal in the reaction chamber than usual, but as I said earlier, the edges of the firebrick below the charge tube look very good, so I don't think they've degraded much; I was thinking that if they had, I'd just turn them around to put a 'virgin' edge back into service, see if it makes a difference, but I don't believe there's enough difference to warrant it.
We'll see. I'm still getting the occasional Stage 3 burn, but also some Stage 2, and lots of demand cycles never get out of Stage 1; yet they complete within 15-20 minutes (175 ->190, with 3-5 degrees overshoot). So I don't think things are running poorly. My wood is certainly not what I'd like to be burning, so that may be a factor as well. Just wish I'd had the wifi remote last year, so I could do some longer term comparisons.