Calibre with SSL, Content Server not loading

Hello, i really like the SSL Feature and its working like it should,
using the https://calibreFQDN:8080/opds URL for external Reader APPS or in the Webbrowser

But using the Main Url the Content Server gets stuck and doesnt load the preview images anymore. Gets timeouts, just shows the book title without picture preview or stopps completly with this message:

Failed to communicate with "interface-data/more-books?library_id=Calibre-Bibliothek", timed out after: 30 seconds

The CPU Load is really low and should be the cause, also the harddisk i/o should. The content server works fine, without ssl.

I tried to set the work count parameter but didnt notice any difference.