I had the same issue with that trade order
, though I used my own backpack that was equipped (I of course unequipped and emptied it) so now in process of making another one see if that makes a diff. Also I've been making timber piles and some piles that I believed I filled with stone (I'm making like about a 100 or so lol) were not, and even one when I then refilled with stone (and was full of wood) the % went above 100 (at least 116) which was weird. Not every timber pile sign was empty of stone but maybe one in ten? (maybe a bit less).
(edited due to confirmed, had a timber pile with 120 % when built, after all the wood in said no stone in put stone in (when it was already 100 %) tried to take a picture of it, but left out inteface which also left out the percentage???
Zee Yesno!