I submitted this one to the dev at github. To sum up, the head dev recommends that qupzilla be upgraded to version 1.8.6. For more info see the bug report: https://github.com/QupZilla/qupzilla/issues/1598
So, upgrade to 1.8.6 then and see if that resolves your issue. For now you will have to accept ~testing keywords, as this new version is not in stable yet.
1.8.6 is now stable