page not found on mobile

when i am visiting the page on my phone and I klick on an event e.g. in the widget at the sidebar, or a “read more”-link – it goes to the page, but tells me “page not found”.
On desktop computers it works fine, and if i tell my computer to act like a mobile phone, it still finds the page. But on my actual mobile phone – it does not work.
Do you have any suggestions on how to work around that?

Best, Johannes

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