When I pick up lane splitters and belt loaders (from the loader mod) they vanish and don't come back to the inventory

Lane splitters break into a normal splitter and belt; this is configurable in startup settings.
As for the loader mod, there appears to be a bug in there somewhere that caused it with one of the last updates. Working on a fix that will be pushed soon along with frozen states on aquilo (optional).

Oh ok, I assumed when you meantion by "break into" is when enemies destroy it