Mobile connection keeps banning app on duckdns

Since 2 days, the iOS app does as above. I can always connect over Wifi, but when I disable the wifi on my iPhone, the iOS app gets banned on IP address.(109.36.142.156) which is the mobile provider.
Not always, immediately after a restart, I can connect, only after a while this gets blocked and banned. Cant seem to find any logic in events for this to happen.

Using a browser window with the identical duckdns address works perfectly.
Has something changed in the app logic?

Ive also tried to delete the app and reinstall, but even that wont help, it immediately loads the old config, even though deleting the app warns one for also deleting all data.