Product backlog refinement meetings take too long.

Our PBR always take too and we end up refining only one or two stories within the given hour. We end up spending too long discussing the implementation detail and as a result I feel we don't get much value out of them. We have tried doing them async but people don't end up reading or just vote very quickly. I feel like we are doing something wrong.

Is anyone, who thinks there PBRs are good and effiecent, willing to dicuss how they do them or share any tips?