I’ve read beans don’t set pods well in intense heat Phaseolus vulgaris & Phaseolus coccienus types don’t set pods well in intense heat. I’ve also read they are known to not ripen seeds fully in shorter climates. (But P. acutifolius is more heat tolerant?), I’ve heard some varieties of Vigna unguiculata do better in the heat but Macrotyloma uniflorum & Vigna aconotifolia are among the most heat/drought tolerant legumes. Worth checking those out.
Might also be interesting to see if your beans set flowers in the shade better?
How many Runner bean varsities have you tried? Might be worth crossing *Phaseolus coccienus x Phaseolus vulgaris to recreate Phaseolus dumosus & select back for more perennial runner bean traits you enjoy (but first step getting it to set seed reliable where you grow it).
Heard of that guy, I’ve even discussed it here before : Lima Bean Landrace Project (Phaseolus lunatus) - #15 by VeggieSavage
Google lens is Wrong! 100% not a Phaseolus spp. because it doesn’t have the classic nutstack hilum (that look like a pair of testicles 
- I know it’s silly but that’s how you distinguish them).
My best guess is these look like some kind of Soybean (Glycine max). Altho I’ve never seen a soybean variety with a hilum highlighted brown. Here’s what soybean hilums look like
Very similar so maybe this might be some other species in the Glycininae subtribe.
hmm… hold up this might be some kind of Pigeon Pea (Cajanus cajan) with it’s hilum outgrowth completely removed but those are usually way much more rounder.
Here’s what Piegon Pea seeds hilums look like
