Factorio Forums

the .log seems to suggest something about the splitters being a bad size.

I was expecting some sort of error message while trying to load the save, rather than an engine crash.

https://mods.factorio.com/mod/nanotorio

I can fix this, but you aren't going to like the fix.

Basically splitters can never be not 2 tiles wide. If you ever break that, it brakes like this when you remove the mod(s).

In fact, I think everything just ends up broken when splitters aren't 2 tiles wide. They are built at a core level with that assumption in mind.

I was more thinking about the game itself having crashed as the issue instead of throwing an in-game error and preventing the "corrupt" save from being loaded.
Errors were pretty much expected / guaranteed in this situation, and i'm sure the belts aren't the only ones.

It makes me think about what might happen if you change the size of a prototype and try to migrate it over previous saves.

In general changing prototype bounding box sizes is fine. The game handles it. For belt entities they aren't meant to ever have more than 1 on a given tile. By c hanging the splitter it breaks the "left tile, right tile" logic and you end up with a splitter on 1 tile. Then you build a belt next to it, and change the sizes back and now the splitter and belt are on the same tile.

Splitters are special in that they are belt-entities but are meant to touch and control 2 tiles. Everything else just touches and controls the 1 tile their center point sits on.