I finally managed to find the culprit of my internet connection issue! So my config in my fresh install 7.1.2 was the same as in 7.0.1 EXCEPT my docker.cfg from version 7.1.3 which I copied onto my fresh install 7.1.2. And this file was the problem for the connection issue. That is also why disabling docker or stopping the array brings the connection back....So I started again with a fresh 7.1.2 install and fresh config folder but leaving docker.cfg this time and voila. No issues anymore.
So comparing both docker.cfg, there are two entries that differ:
DOCKER_ALLOW_ACCESS="yes" was added in the 'broken' docker.cfg and DOCKER_AUTHORING_MODE="yes".
Disabling "Host access to custom networks" in Docker Settings removes DOCKER_ALLOW_ACCESS="yes" and solved the issue for me in 7.1.2. I can't tell if the solution works also for 7.1.3 but its worth a try.
Maybe this setting broke something in 7.1.2 and 7.1.3