Yeah, this is similar to my bug with the “Storage Full” icon on the TP : [BUG] Trading Post storage is full icon appearing when it clearly is not full
It is sporadic in my game now- it stayed for a year or 2, then disappeared, and comes back and disappears again every now and then. IIRC, this bug was around when the game was first released, it got fixed, but it’s back again. Not that unusual in games and other SW- fix one bug, but because of one conflict or dependency buried in thousands of lines of code- specific sequences of actions or conditions met causes an unexpected bug like this. And they are a pain to try to track down, untangle, and get fixed.
I am just roleplaying it as- the rat catcher next door has a weird obsession wth collecting rat teeth, and is filling up the bins in the TP with them until the traders notice and pitch them all into the nearby lake. 