I think we are seeing two different things here. First one is that inserter should certainly drop its hand contents if it can do it immediately. This is behavior that most people did complain here about and which is used all over the place. And the second one is the problem which arises only with t...

Hit this exact message today in v0.13.17, both trying to advance after level 4 and directly launching level 5. Checking the lua files, level 5 is trying to use fast-inserter and filter-inserter, and those don't have prices set in tightspot.lua (previous levels currently use stack-inserter and stack-...