I built an aquatuner inside an insulated room using existing abyssalite for some of the walls. The aquatuner was used to pull heat out of my base and deposit it into a small amount of water (to produce steam for rocket fuel). It worked fine for a while but one cycle (when it was around 150C and 130kg pressure) it randomly all liquefied back into 90C water. Looking at an autosave file before it happened, I noticed that the mass of the water had significantly increased. I could pretty consistently recreate the bug by just reloading my auto save, but it varied in how it happened. I noticed the temperature drop was occurring because water would magically appear inside of my insulated room causing a near instant drop in water temperature (leading to condensation if the temperature drop took the water below 100C). If the temperature didn't drop below 100C the new water became steam significantly increasing the pressure of the steam.