So, I was watching an episode of ATK (Season 21 Episode 17 here:
https://www.americastestkitchen.com/epi ... -favorites) where they were making peanut butter cookies. During the segment, the cook mentioned that adding water to peanut butter will make the peanut butter cookies dry and crumbly. The way I understand the explanation is that peanut butter is mostly fat with protein suspended in it. When you add water to the peanut butter, it interferes with the suspension. It sounds similar to how chocolate seizes when you add a water-based liquid.
Based on that episode, I would try adding less water or a little more fat to the cookie dough.