Page crashes because of Page Parameters

Hi guys,
I am currently working on a web app. This app receives data via an API which is then displayed on a page in a list. When I press on a list item and want to navigate to another page, it crashes. The ID of the list item is taken from the data variable and forwarded to the page variable via a formula (STRING ( The web app crashed and I was redirected to the start page.

The reason for the crash is the page parameter, but I do not know how to fix this