Perhaps this has been addressed already, but I did notice upon my first playthrough of ES2 a slight glitch in the 'Trade Approval' bar that appears when trying to convince another Empire (the Vodyani) of a trade. I was looking for Dust, and suggested that they just give me 200 Dust. Naturally, they were very upset with this propisition so I offered 20 Jadonyx, which they were apparently deeply in need of as the approval bar shot up from all the way in the orange to all the way in the blue. Naturally I wanted to see how much Dust I could get for my (rather large) stash of Jadonyx, so I upped the amount of Dust I wanted to 500 while still offering 20 Jadonyx. Their approval of this dipped slightly but nonetheless they were positively in favour of the deal. Again I went to toy around with how much Dust I could milk off of the kind of Vodyani and I doubled the amount I wanted to 1000. The game processed this for a bit and after it told me that the Vodyani would be more than happy to give me 1000 Dust for a measly 20 Jaodnyx I hit 'Make an Offer'. 

The game then processed my offer and I was met with a harsh reply from the Vodyani, who asked me how I could dare suggest such an unfair exchange. 

I don't know if this glitch arose from me changing the values of the trade goods too quickly (as I did also toy around with how much Jadonyx I wanted to give as well as how much Dust I wanted) and it's by no means game-breaking, but I thought it might be worth bringing to the attention of the Devs at any rate.