Hello,
Thanks for reporting the problem. I can reproduce the problem on your website but I don’t know the cause of this issue for the moment. Nimble Builder shouldn’t normally generate 404 error after paginating a given number of page. For example, I’ve created an example paginated post grid on this page : https://nimblebuilder.com/paginated-post-grid/, which display posts properly after page 6.
The only thing I can recommend is to follow the usual troubleshooting steps, in order to isolate a possible conflict with a third party plugin for example : https://wordpress.org/support/topic/%e2%9a%a0%ef%b8%8f%e2%9a%99%ef%b8%8ftroubleshooting-steps-for-nimble-builder/