The items are set as "not-sendable" to orbit by default, so I'm really not sure how they would be ending up as a payload... My best guess as to what is happening is that when the recipe switches, the inserter gets confused as to where its dropping a number off, but I really just do not understand what's going on here, and I couldn't figure out how to reproduce it.
I'll keep thinking on this, though. Thanks for bringing it up.