Could be slugs & snails. I've caught them eating holes in mine. If there's a faint shiny white film left behind (dried slime) then it's them for sure.

My experience with Japanese beetles are they are only on the vegetation for a couple of hours and then go away until the next day. Usually they are around in the afternoon and then gone in early evening/late afternoon.

It can't be snails or slugs. These are pole beans and I've never seen snails and slugs 5 feet above the ground.

I have, but I agree that they usually only go for the lower leaves & stems.

Ditto on the previous two comments... if the vines have already been climbing, slugs or snails are unlikely to be the cause. Their trails would be visible. A photo showing the damage might help, if you are able to post one.

Having eliminated JB as a possibility, my two best remaining guesses would be grasshoppers, or Mexican bean beetles. In my experience, grasshoppers seem to prefer the higher branches, and chew large holes in the leaves (caterpillar damage is similar). If MBB is the problem, the damaged leaves would have a net-like appearance, and you should be able to find some of their larvae by checking the underside of the leaves. Both can cause severe damage if their population is high.

If the damage is only minor, there are quite a few other insects which could be the cause... I have frequently seen spotted cucumber beetles on my beans, but never in large numbers. Some leaf damage is inevitable; but unless it is severe, or the beans themselves are damaged, it may be that no corrective action is necessary.