Traders keep leaving goods behind. 2nd world and fortress this is happening.

Basically the above. I created a new world and fortress and first trader, after trading, left a little while later and didn’t take any of his stuff. Finally took trade depot down to get the stuff after it sat there all winter. Trader came back in the fall again and did the same thing, but I was not getting any immigrants. Decided to start another world and fortress and try it again and it just happened again. I have played DF on and off for a few years but I have never have this happen before. Potential bug? I don’t think I am doing anything to cause this.