That is strange indeed. A few thoughts
Do make 100% sure you tested with ALL non weaver plugins disabled.
Are you using a child theme? If so try without it in case something in the child needs to be updated.
If you create a test page based on the page with posts, with all default options, do you have the same issue
If you have the weaver Show posts plugin installed, try creating a test page based on the default template, and add the posts using a weaver show posts shortcode (after you create a show posts filter), and see if the same problem appears there.