We cannot switch the theme and deactivate wpml now, because our customers using the site for booking.
A few: Honeypot, Mailpoet, Statify, popup Builder, Updraft Plus, Yoast SEO, Yoast Duplicate Post.
Also some from our theme The7: WP bakery, Go Pricing, Elements, Slider revolution.
And WPML Multilingual CMS, String Translation, Sticky Links.
For testing reasons I deactivated all, except from WPML, whcih doesnt change the behavior. Because our customers use the site for booking, I couldnt deactivate WPML. So it could maybe WPML. But I don’t understandd how this causes the problem.
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Setup is correct and the same in our other page, where it works.