Green Bean pest?

It's the start of the season and will be a couple of months yet before we're able to plant our pole beans. Had an issue last year that I have never had in my 30 years of gardening, so wanted to see if any of you have had this issue and, if so, what you know about it.

Some of our vines started dying off well into the growing season. Other vines on the same teepees were just fine. Turned out that the dead and dying vines had been "cut" about 2-3 inches above the soil line. I've never seen this. I figure it is some kind of insect, but found nothing out of the ordinary on any of the vines as far as critters go. Hoping it doesn't happen again this year, but just in case, anyone else have this problem and get it figured out?

Thanks!