How Do I Fully Flush Cached Redirects From Safari?

I have a device with a web-based control panel, and accidentally set it to redirect all http pages to https, even though some don't work over https. Although I've since corrected this, Safari seems to have memorised the redirect and is refusing to forget it, instead constantly attempting to redirect me to the invalid https address. I've already closed Safari, cleared ~/Library/Caches/com.apple.Safari/ and ~/Library/Cookies/HSTS.plist but it still seems to be remembering the redirect when I re-open it. Where else could Safari be storing this information? I can access the correct page via Firefox or Chrome, so it may not be a system wide service, or if it is it's not one that the other browsers use. Unfortunately because the web-panel is provided by a device I don't believe I can adjust headers or setup a redirect back to the correct URL, which seem to be options offered in other similar questions, so I really need to find out where this data is being stored so I can destroy it with fire.