How do I resolve the feud between Trumbel and Sweynur?

I'm doing the "Against the grain" quest at the moment. I've talked to Sweynour, I've talked to the miller Trumbel. I talked to them again. I'm supposed to somehow resolve the conflict, but I only get the same dialoge options I already exhausted again. I'm supposed to convince Sweynour that the miller doesn't have any grain stashed away, but I only get the option to tell him that I'll talk to the miller, which I already did.

Am I missing some step here in solving the issue? What do I have to do to advance the quest?

You have to talk to Pasca (the innkeeper/bartender) to order drinks for the famers. Took me quite a while to find that one. I was just carrying beer and ale in my inventory and wondering why it wasn't working.