https://developers.facebook.com/tools/debug/
I used the Facebook Open Graph Debugger to solve the issue. On the very bottom there is a link called
Scraped URL See exactly what our scraper sees for your URL
This shows exactly what Facebook catches as code and there was a print of a paragraph-tag from one of the libraries I have been using. I can only recommend to debug it this way because I wasted a lot of time not doing so (because I did not see the link at the bottom of the page).