Hi Pascal,
I’ve disabled Rank Math on the staging area of our website which is at #. I’ve temporarily disabled the HTTP Auth on it so you should be able to access it without problems.
When I look at for example this page: #
I can see <title>World Markets Review – Smart Options</title>
in the source which is not the case on the live site. So it seems that Rank Math is causing this problem.
I’m gonna contact the Rank Math support as this is obviously an issue with that plugin and not with the AMP plugin.
Thank you for pointing me in the right direction!
Kind regards,
Richard