I don't know if this a feature or not, but with a right timing you can make Drop Pods available on the trading screen.
Ver:651
I sold something to a trader, and checked another one. When I was at the bottom of the list I noticed that I have 2 drop pods to sell. Unfortunately the trader didn't want to buy them. :)
[attachment deleted due to age]
Just saw this last night, and was amused.
That only happens when you close a trade window and reopen it just after a purchase. The prior trade sends the goods via drop pod and it lands on trading beacon area then takes a few clicks to turn into bought item. Not a bug just you catching it as you reopen trade window.
As mentioned above, not really a bug, but an exception rule should be set up to not make it show up on the trade screen imo