Just update and start a separate world where you force yourself to do everything with conveyor belts and trains!

I think I may do so when I get the new update if they haven't released 0.10.5 or whatnot yet.

Well I loaded from the same save I had earlier, and did basically the same things and they worked fine. So I'm not sure what the problem actually was...

I'm not entirely sure what happened to cause it, but the splitters don't seem to "connect" to each other anymore. They filter properly until they get to something they're supposed to send to another 'lane', and then it just gets stuck.