All autosaves have the same issue, and were all created during my earlier play time.Notice
Corrupt map: trying to load already loaded heat buffer. heat-pipe at {409.5000000000, -212.5000000000} is trying to load index 319 but it's already loaded for heat-pipe at {378.5000000000, -205.5000000000}.
Closest existing bug report I could find, marked as resolved: [0.18.4] Crash: HeatBuffer::HeatBuffer viewtopic.php?f=11&t=81141
In my current map, I do have nuclear power with heat pipes up and running, but those have been built and steady for multiple real-life days, and I've successfully loaded the map several times since then, until now. I've also successfully loaded previous save files without issue.