I'm having an issue with the pdf printout of invoices missing header, footer and layout. I've had struggles with wkhtmltopdf in the past so I thought that was the culprit again. However, after further investigation, is seems to be something else. What I've found:

• When I print an invoice, there is no layout (as mentioned)

• This is also the case when I print to html (so it's not pdf-conversion issue)
  

• When I print a sample report (Settings > User > Companies > <Company> > Report Configuration > Preview External Report) the header/footer and layout are OK.

• When I compare the html of the sample report and the invoice, I see that the latter has only two stylesheet references, while the former has 7:

sample report:

            <link rel="stylesheet" href="/report/static/src/css/reset.min.css" type="text/css"/>
            <link rel="stylesheet" href="/web/static/lib/bootstrap/css/bootstrap.css" type="text/css"/>
            <link rel="stylesheet" href="/website/static/src/css/website.css" type="text/css"/>
            <link rel="stylesheet" href="/web/static/lib/fontawesome/css/font-awesome.css" type="text/css"/>
            <link rel="stylesheet" href="/base/static/src/css/description.css" type="text/css"/>
            <link rel="stylesheet" href="/report/static/src/css/report.css" type="text/css"/>
            <link rel="stylesheet" href="/stock/static/src/less/report.assets_common/report_location_barcode.less.css" type="text/css"/>

Invoice:

            <link href="/web/content/1102-9a5a204/report.assets_pdf.0.css" rel="stylesheet"/>
            <link href="/web/content/3818-3a3cb81/report.assets_common.0.css" rel="stylesheet"/>

Does anybody have an idea what might cause this?