Can not delete field

In my form 'Asset' the field 'Assigned_Player' can not be deleted.

When I try, I get a message listing various places where the field is supposedly used. But it is not. To make sure, I downloaded the whole app as script and searched for the field name. I found only some views and the field itself.

Edit access for support is enabled.

Thanks for looking into it.

Regards,
Filip