Custom fields for individual using tab with table causes 404 not found for popup
Try switching your theme to WP Twenty Seventeen or something basic like that.  I tested "Tabs with Tables" on my install (Civi 4.7.23, WP 4.8.2) and in the Civi Sandbox (Civi 4.7.26, WP 4.8.1) and they both worked. If it works with the different theme, the simple fix is to temporarily switch themes when you need to edit these. Hopefully that is not very often. I have a conflict with my theme in a similar area.