Can not delete field from Custom fields in Custom Profile in back end!

Hi Support

When I go to profiles/custom filed and try and delete a particular field for eg "Blender" I can not!

"Blender" (I only have one guy with "Blender" so I am using this as a test) I can not delete this!

I added a test field "Delete me if you can" I also can not delete this!!!

This what happens eg:

Try to delete "Blender” from the custom fields menu: it disappears in the back end but reappears after I save. Ditto "Delete me if you can"

thanks

Paul