WiFi strange issue

REPRODUCIBILITY (% or how often): 100% / permanently
BUILD ID = OS VERSION (Settings > About product): 3.4.0.24
HARDWARE (Jolla1, Tablet, XA2,…): XperiaX (single sim)
UI LANGUAGE: german
REGRESSION: (compared to previous public release: Yes, No, ?):

DESCRIPTION:

When using my wifi at home, I am unable to reach one specific webpage (zdf.de), I immediately get a server not found error as if I do not have any network connection at all. All other addresses I have come across have worked so far.
I have the same Issue when trying to sync my mails via the app (one account via my provider vodafone and one via google), I get an instant sync fail. However, i can reach google and google mail via the browser without any problems.
Also I am not able to update the weather app - no network connection - but I can access the foreca page without any issues.
A simple reboot of the phone does not help, have tried this multiple times.
I am not exactly sure, when this issue appeared, but I would say within 1-2 days of updating to the latest version of 3.4.0.24.

I do not have these problems when switching to mobile data (4G) or using a different mobile device in my wifi (e.g. Laptop, tablet, iPhone etc.)

PRECONDITIONS:

STEPS TO REPRODUCE:

EXPECTED RESULT:

ACTUAL RESULT:

ADDITIONAL INFORMATION:

(Please ALWAYS attach relevant data such as logs, screenshots, etc…)

So I have done some further research with different devices and it turns out that this was not a Sailfish Issue but more an issue with the DNS-Server in my router - my bad!

Just in case anyone else experiences this sort of problem. nslookup in the terminal shows you which DNS is in charge.