Connectivity issues related to IPv4 addresses while IPv6 works

REPRODUCIBILITY (% or how often): Seem to be random
BUILD ID = OS VERSION (Settings > About product): 4.2.0.21 (Verla)
HARDWARE (XA2, X10, X10 II, …): X10 II
UI LANGUAGE: Finnish
REGRESSION: (compared to previous public release: Yes, No, ?): ?

DESCRIPTION:

I have rencently using only mobile connection with my phone to see if it would help the connectivity issues when changing between wifi and mobile connection.

Now I have few times came to a strange issue where some sites work but some don’t. For example testing random bigger pages around the world like google.com, yandex.ru, bing.com and hs.fi seem to work and reply but at the same time for example blocket.se, apple.com, ebay.com or reddit.com do not.

When I start a terminal and try to ping or traceroute the pagest that do not respond, they are all replying with IPv4 addresses and with message “Network is unreachable”. The ones that do reply are all exposing their IPv6 address.

It does not matter whether I use jolla browser or firefox as both of them work/do not work with the same pages. There are similar issues also with different softwares. Protonmail-client is unable to connect to the server and at the same time the finnish teletext application is working.

PRECONDITIONS:

Use mobile connection without WLAN.

STEPS TO REPRODUCE:

I cannot be certain but restarting android support, restarting network stack, reconnecting to mobile network seem to cause this sometimes.

EXPECTED RESULT:

Browse, ping and traceroute all sites as usual and receiving response

ACTUAL RESULT:

Some sites work and some sites don’t.

ADDITIONAL INFORMATION:

Added a sample image, hs.fi replies as it uses IPv6, apple.com fails with IPv4, yandex.ru replies with IPv6 and ebay.com fails with IPv4