Custom gitlab-runner with non root user, shows 400 bad gateway in log

we are using a custom gitlab-runner on kubernetes and latest images. When using a non root user, the log shows:

e[37;1mFeeding runners to channel e[0;m e[37;1mbuildse[0;m=0
e[37;1mChecking for jobs… nothing e[0;m e[37;1mrunnere[0;m=2msWMYfR
e[0;33mWARNING: Checking for jobs… failed e[0;m e[0;33mstatuse[0;m=400 Bad Request

when using the root user there is no bad request message in the log file.
question a: how to get rid of the error message without using a root user ?
question b: why does the log file show weired characters ?

thanks in advance,