Copying and/or centering throws code at the top of

I have found the cause : the plugin System - VM OG Meta Tag
it automatically adds a meta tag based on your article content, but without triggering the content plugins. This takes the code of the page, like it its. This is not correct
disable this plugin or try to give a custom meta to your article

Thanks Ced. I've used that plugin for years and these are the first times I've had the conflict. I think I'll just start adding the OG tags manually.