background images do not appear on mobile devices

I customized Astra Theme. Everything is working fine on desktopo, but on mobile devices some pages (HOME, QUALIFICHE and SERVIZI) don’t show the background images at all, or (see home page) they appear as small repeated miniatures. I already checked that the “do not display on mobile” button is off and the images are loaded in all responsive options.
How can I solve the problem?

The page I need help with: [log in to see the link]