Fix LiveCanvas save-corruption on WordPress (PicoStrap5 theme)

I need an experienced WordPress developer to fix a save-corruption bug. Saving any page in LiveCanvas destroys the layout: the header duplicates, the hero and its Gravity Form get stripped out, and the page collapses into the footer. It happens on the live home page and on a duplicate page, so it's theme-wide, not one bad page. Setup: WordPress on SiteGround, PicoStrap5 child theme, LiveCanvas, WPCode, Gravity Forms, WP Rocket. My host found leftover output-buffering code in the theme's functions.php and commented it out, but saves still corrupt, so something else is rewriting the page output on save. Deliverable: find the true root cause and permanently fix it, proven by a clean test save that leaves the hero intact. Rules: work on a staging copy only, back up first, and no changes to my live site between 8am and 6pm Pacific. To apply, tell me in your first reply what you think is intercepting the save and whether you've fixed LiveCanvas or PicoStrap issues before. Generic pitches will be skipped.