Apologies if this is obvious, but I can't get my production lines to work in the sandbox as inserters won't pull items off the belt and into machines.

I can use the infinite chests/loaders fine to make things like Iron and Coal, and the inserters will pull those items off one belt and onto another built, but they will NOT pull the items off a belt and put them into smelters, assemblers, etc.

I've never seen this before, and I don't think that this mod does anything that would cause that. I'd bet there's some other mods causing this issue. I'll need your save to attempt to reproduce this.

Ah good call, you're right, I cleaned up my mod list and that seems to have fixed it. It seems to work with all the mods I actually need so probably not worth pinning it down, appreciate it!