I'm writing some extensions for an old 4.7 typo3 installation. After copying my changes from a test installation to the live system, the Ajax overlay and spinner doesn't disappear in the Typo3 Backend. I see no errors are in the JavaScript console.
The content is loaded, I can manually hide the overlay with the debug tools of the browser. In Chrome everything works fine. I cleared the typo3 cache and browser cache and truncate the temp folder.
Any ideas what I can do?
sorry to say, but:
don't support anything for those old installations by updating extension or even write new extensions.
Those old installations have no support to the behaviour of the new browsers.
You just run into such a browser behaviour change. Nobody (except you?) will fix the behaviour in the javascript of the old core.
If you want to help the owner of that old page, help him to upgrade the site to a supported version
and then write a new extension!