Extremely high temperature for igneous rock and infinitely spawning.

I have no idea what causes this, but I did have something similar with dirt in one of my rooms. The fact there's a block just above it is not one of the reasons, mine happened in the bottom-right corner of a room about 9 tiles high, and mass increases by 1g/s. It also cannot be swept fully, it will always keep some mass.

Do any of you have a save which reproduces the problem? That would help us a lot in tracking this down.

I have a save with the jumping dirt glitch. It happens pretty consistently in all my games, usually on front of the compost or above hot igneous rock or liquid phosphorus. I think with the phosphorus it's the result of phosphorus gas continuously condensing into solid igneous rock when it hits colder gas. Never seen it just in the middle of a base though.

It's the two clumps of dirt on the right side of the chlorine filled room.

A few of my other reported bugs in this save file too.

Jumping Dirt.sav

Here's another one that's even more similar with falling dirt that's overheated (but more like 110C not 2000):

Of course, the problem seems to stop after save and reload so not sure if the save file will be as much help as you'd like.