Started using this mod, and am putting a lot of items through it (because of another mod that makes lots of byproducts). I noticed that sometimes the landfills get stuck. Tried waiting for about 20 minutes before I gave up and emptied them. Over time they stop completely.
I think it might have to do with adding items before the landfill is completely emptied (by the deletion function). It seems to delete only part of the inventory, then my inserters refill it, and sometimes it deletes the same part of the inventory about 4 minutes later, sometimes it doesn't. When it doesn't it never deletes the items, they just sit there indefinitely.
That's odd.. My code is supposed to account for more items being added in over time. The code does need a complete rewrite, as it is no where near my best work. If you could send me a save file over the forums, I can try to debug the problem. Thanks for the report.