I’m writing for the same problem with the background image not responsive. I contacted the “Site Origin” plugin author 19 days ago but until now we have not received any answer. 🙁
Unfortunately we can not present online the site as now and we ask you to help us, please.
Also we like some advice about a new plugin for a responsive parallax as now by desktop or a new html.
How we can resolve the issue?
Please help us!