I’m very familiar with reCaptcha and manage over 50 sites which utilize it, with much higher profiles and traffic than the one I have your SF plugin installed on. I understand this is NOT an easy problem to troubleshoot, but please consider there may be some kind of vulnerability with the way you’ve implemented it. It could be that there’s absolutely nothing wrong with your implementation, but in my case, I’ve not seen an increase in bot spam through reCaptcha implemented in any other site I manage – using custom code, Gravity Forms, CF7, WP Cerber, WordFence, etc.
Thanks for your consideration. All the best to you.