I added a metabox via the builder, saved it and was able to see it on the page edit screen. I then:
-disabled the show/hide and conditional logic plugins as I did not need them
-added a few more fields to the meta box
-limited it to a specific custom post type
-refreshed the custom post type entry I was working on and they were gone.
I undid all of the above except removing the new fields and they are still not appearing
I can send credentials if you'd like.