Sawmill will delete items if they don't fit in the output, and will continue to process when it's full, deleting items.

if the sawmill output cannot fit the new items it simply deletes them. This is made worse by the fact the sawmill continues to process items even when said output is full.

You can see in the video the ironwood plank stack gets to 19, it crafts 3, stack gets to 20. Then continues to process and they are deleted as the chopped wood takes the slots.

I’ve checked all storage, characters etc. and confirm it was deleted in this process.

Good idea is to reduced the chopped wood amount from ironwood.