Delete selected fields - payment method - admin area

Hello guys, I need you help with Payment method in admin area. I integrated new online payment module. Then I added field (ADD FIELD) to payment method connected with this module. Unfortunately it is mishmash of letters and symbols. So I wanted to delete it but I can’t. When I click to DELETE SELECTED FIELD nothing happens. Only the text is bigger now (…amp;amp;amp;amp;…) I also tried to add another filed and delete it. It works fine. But I cannot delete the first field. Is there any chance how to delete it? Or remove that payment method connected with the module?

In Phpmyadmin, table oxpayments you can edit the payment and clear the field OXVALDESC.