I have a copper volcano surrounded with ceramic insulated tiles. There's a 150kg layer of petroleum on the bottom, the rest is steam. Sweeper arm, tempshift tiles, some automation, and steam turbine on top round out the system.
After watching the volcano for a while, I noticed a weird bug. Sometimes when the copper volcano erupts, the resulting copper debris cools quite quickly (due to the petroleum layer on the bottom) as expected. Sometimes though, and I don't know what triggers this, it will cool at around 1/10th to 1/20th the usual rate. Instead of cooling to 130ish after 1 cycle it was cooling only to 400ish when this bug occurred. In fact if you watched closely you can see it switch from cooling at a rate of 2-3C per second to 0.1C per second.
This happened sporadically but consistently. If I paused the game when the copper was cooling slowly, saved it, quit to the main menu and reloaded, the copper debris would return to its normal (fast) rate of cooling. Also using the sweeper arm to relocate the copper (activating/disactivating the sweeper arm quickly so as to cause it to drop mid 'pick up' and hence relocate the copper) still within the chamber and the copper would reset to its normal/fast rate of cooling.
Steps to Reproduce
I'd upload the .sav file, but apparently it won't let me?
This issue has not been confirmed by a developer yet.