I came here to report the same issue. On stadia. In barter when I select an item everything else vanishes. I have to sell that single item and then switch to trade and back to barter to be able to sell another single item. Terribly frustrating. Here's a clip showing the problem.

https://stadia.google.com/capture/9455512d-81c2-4dcf-b438-5631a968e545

Shaolin Stoner