It seems that if an item spoils whilst it is stationary in a splitter it does not get moved by the splitter. Picking up even one item will then get the splitter working again and belts flowing.

Want to enjoy learning the new mechanics at my own pace so I'm thinking of a peaceful first run before second run having enemies turned back on (I can't just say biters anymore!). Anyone else in a similar mindset?

If you are playing with sound enabled (or are able to hear) then it is easy to tell when turrets have engaged and/or buildings destroyed, as you get an alarm as well as the small warning triangle and arrows. If you do not have sound enabled/are not able to hear, then when focused on the task at hand...