I just talked to the Rube and after going through a few offers he started to walk away. I pressed the arrow keys to follow him but couldn't move, then noticed my screen was moving with him (the offer dialogue still in the middle), I continued to go through offers as he went to the edge of the screen, then back and his dialogue greyed out a little when he passed me, the option I'd pressed had a little loading wheel. He kept walking an then vanished, the offer dialogue stuck in loading (so I couldn't press anything) stayed at the edge of the screen and I was still unable to move. Had to close and restart the tab.
This makes me wonder if there is a limit to the number of offers you can go through with the Rube?
I also noticed that if your inventory is full he doesn't want to talk to you. Had this happen once and someone else talked to him instead before I could clear a space (I'd really prefer it if he talked to you anyway so you could drop/consume an item while he was making offers, and if you still didn't have room he could drop the traded item on the ground).