Divi frontend doesn't appear on assigned template page. "Uncaught TypeError"

Hello. I created two separate templates, one header-footer and another for body. After applying the header-footer for all pages and the body template to specific ones, I cannot load the divi frontend builder anymore when I 'Edit with Divi" the pages with the body template. This seems to have happened overnight after installing a maintenance mode plugin, which I promptly deactivated. The builder won't load anyway.

There are no scripts nor particular codes on the body template page settings and sections. There's just one parallax script injected on the header site that never gave me any issue.

The web console reports what you see on the attached image (Chrome and Firefox). While the frontend of the footer-header throws only the "Uncaught TypeError: $(...).children(...).size is not a function" error

I tried everything I could find suggested on here and elsewhere, purging any type of cache - CDN, Cloudflare - browser, WP, databases -, using divi safe mode, checking divi support center, deactivating both dynamic CSS and static CSS generation (they have always been deactivated as they break pages), manually reinstalling Divi, enabling/disabling jQuery Migrate, WP memory limits and sizes already increased, using other browsers, deactivating the other plugins, using old Divi Classic version (appears but won't load levels). I do not know JavaScript, so I don't know what the error means honestly. The theme builder of that template works normally. Thank you.