My Intel NUC Kit NUC6CAYS frequently goes offline / down

To fix above error, I have applied the 1st solution (2nd solution didn’t work for me) proposed in https://stackoverflow.com/questions/52395512/why-does-bitbake-error-if-it-cant-find-www-example-com
So I added the following 2 lines to the end of ./layers/poky/meta-poky/conf/distro/poky.conf
(note that as no editor is installed, I also installed nano)

# The CONNECTIVITY_CHECK_URI's are used to test whether we can succesfully
# fetch from the network (and warn you if not). To disable the test set
# the variable to be empty.
# Git example url: git://git.yoctoproject.org/yocto-firewall-test;protocol=git;rev=master    
CONNECTIVITY_CHECK_URIS ?= "https://www.google.com/"

… but now I am getting follow error:

[000000001][LOG]This might take a while ...
ERROR: /workdir/balena-intel/build/../layers/meta-balena/meta-balena-common/recipes-containers/docker-disk/docker-disk.bb: docker-disk: Docker needs to run on your host and current user must be able to use it.
ERROR: Failed to parse recipe: /workdir/balena-intel/build/../layers/meta-balena/meta-balena-common/recipes-containers/docker-disk/docker-disk.bb

Summary: There were 2 ERROR messages shown, returning a non-zero exit code

I have no clue how to fix this. I have added user pokyuser to docker group but this didn’t fix it:

pokyuser@ae30fa5181cf:/workdir/balena-intel$ groups pokyuser
pokyuser : pokyuser sudo docker
pokyuser@ae30fa5181cf:/workdir/balena-intel$ 

So, I have no clue how to progress and I am certainly not sure that I am following the right track for building a balena OS as I have encountered already several problems.