This appears to be happening because map generation gets 'activated'. Even if I stand still, the map generation continues to run, as far as I can tell indefinitely.
Having RSO as part of the save sometimes makes it even worse, and sometimes doesn't.
Either way, I am curious why map generation is running when I am not near the edge of the world. I can definitely move *farther* from the edge of the world and make the map generation stop completely, so it must have something to do with how close I am to the edge of the world. But I am not particularly close - I cannot even see the edge of the world in the minimap.
Basically, it makes doing work far from my base much harder than doing work near my base, which is pretty unintuitive.
I am not at all sure this is a bug - it's quite possible this is just some requirement of how map generation works. On the other hand, when I am actively revealing new tiles, it gets much worse than this, so obviously there is a difference between this type of map generation and the 'real thing', where I'm actively seeing new tiles get revealed.
Obviously, it would be nice if the game could run at 'normal' speeds when I am not actively exploring new parts of the map. But if this is necessary to the way the game works, I understand.
No map generation running -- 57 UPS

Map generation running, only a few steps north (toward the edge of the world) -- 36 UPS

Same map, different location, but also far away from main base.... RSO mod not actively taking time, but map generation still running -- 46 UPS

All screenshots in imgur album: https://imgur.com/a/1Hzo2
savegame and mods: https://www.dropbox.com/sh/vb475cno8eon ... IYpya?dl=0