I have something I cannot resolve : this string : "); appears on the top left corners of pages. It seems that it appears during loading but sometimes it stays on the page like here :
There’s a fun diagnostic technique called “trash and bash”.
Make a copy of your app, confirm the problem occurs in the copy. The following operations can be done on the copy until the problem is gone or there are no more items left.
Delete HTML elements.
Delete HTML / javascript in the app’s Settings > SEO & Metatags.
Delete other elements on the page.
Uninstall plugins.