Thank you for your question, Greg.  There are over a dozen diseases which are known in the bean family, most of which cause wilting of foliage.  However, it is unusual for the wilt to be inconsistent in the plant.  Assuming that the plants are getting adequate water, the plant tissue furthest from the roots would be impacted first.

Have you checked the wilted leaves for insects?  Aphids, especially, suck out the chlorophyll from the underside of leaves.  They also are found along the stems.  This article has more information about this pest and its impact on plants:  https://ipm.ucanr.edu/agriculture/dry-beans/aphids/#gsc.tab=0
Please let us know if you discover any indication of a pest infestation.  Thanks!

Thanks, Greg.  If we rule out insects and inadequate water, what's left is fungal and bacterial infections, described here:  https://s3.wp.wsu.edu/uploads/sites/2054/2014/04/FungalandBacterialWilts.doc

I suggest that you send plant samples to the OSU Plant Clinic for examination:  https://bpp.oregonstate.edu/how-submit-plant-materials

I hope they can help.  Good luck!