Can’t set Statistic variable for player positions

I am trying to create player positions (Milfielder, Goalkeeper, defender, etc) with statistic variables (Offense/Defense) but they are never saved. The positions are created with no statistic variables and when trying to edit position they also dissapear after saving… This happens with every single position except for the 4 default pre-built positions

The page I need help with: [log in to see the link]