I had some issues with handheld cappers and certain bottles. The consensus on the forum and at my local home brew store was to get a bench style capper. I haven't used it yet, but the difference in design makes sense.
I have 2 types of crowns and apparently 2 types of bottles. The crown on the left will only go on to the left bottle. The crown on the right will go on either. I can't figure out why?