Default [Q] After adding a CA certificate, I can't set my previous lockscreen setting

After adding a CA certificate, I can't set my previous lockscreen setting: just slicing to unlock. It has been disabled. It says: "disabled by admin, or certificate storage."

I've tried deleting my custom CA certificate (used for a proxy server), but Slicing lock feature keeps disabled.

I saw there was a solution, but is there a way to fix it without root?