For now, the export service is using the phantomjs to emulate the page on the server-side, and after that, the page is exporting to different formats. Unfortunately, the phantomjs has some difficulties with displaying images, and there is no easy way to fix it.
The only workaround I can suggest you, for now, is to change or remove the background image for the
.dhx_scale_holder and use some different background during the export, it may look like follows:
Here is a demo:
Or you can use the PNG export(which works correctly) during the issue will be fixed.
We currently working on update the export service and in the future, this issue will be fixed, unfortunately, I can’t give you any ETA.
I will post on this topic when the export service will be updated.