Added about 40 mbar 4He to mixture on Monday, then tried to cool again. Couldn't cool below 0.4 K

Fridge behavior suggested that the problem was not anything to do with circulation, but rather some new heat source

Hypothesis: there's He in the IVC, and warming the 1K Pot to add new mixture caused it to shift around to somewhere where it caused a thermal bridge

We stopped circulation and boiled the bath away, warmed the MC to about 12 K, watched the IVC pressure - saw an increase and pumped this away

Did another LHe transfer yesterday

Start circulation again today: cooling down well, currently MC<30 mK.