Happened to me as well, developed a website for a client and they started to get that malware warning on a specific page. there was absolutely nothing special

Happened to me as well, developed a website for a client and they started to get that malware warning on a specific page. there was absolutely nothing special about that page except the content, I noticed that the content included words like "Visa, passport, license etc .." so Google classified it as a probable scam. after a few submissions, I think the page got whitelisted. its very annoying indeed, especially that this functionality is now built into the primary browser.