point_of_sale.report_receipt can't be printed, this error comes:

Uncaught SyntaxError: Unexpected token I in JSON at position 0http://192.168.10.156:8070/web?debug=#id=525&view_type=form&model=ir.actions.report.xml&menu_id=83&action=73:1ZurückverfolgungSyntaxError: Unexpected token I in JSON at position 0 at JSON.parse (<anonymous>) at HTMLIFrameElement.<anonymous> (http://192.168.10.156:8070/web/static/src/js/framework/ajax.js:228:40) at HTMLIFrameElement.dispatch (http://192.168.10.156:8070/web/static/lib/jquery/jquery.js:4641:58) at HTMLIFrameElement.elemData.handle (http://192.168.10.156:8070/web/static/lib/jquery/jquery.js:4309:63)

Why is this ? Can someone help me ?

Where can I change this template? :

How can I set this to format A4 ????