error parsing HTTP 403 response body: invalid character ‘F’ looking for beginning of value: “Forbidden\n”

To fix this Gitlab error please edit your /etc/gitlab/gitlab.rb file and update your whitelist with

gitlab_rails['rack_attack_git_basic_auth'] = {
'enabled' => true,
'ip_whitelist' => ["127.0.0.1, x.x.x.x"],
'maxretry' => 20,
'findtime' => 60,
'bantime' => 360
}

Replacing x.x.x.x with the IP you are trying to login with.

Then do gitlab-ctl reconfigure

Bonus round, also docker login -u <your username> -p <token> registry.gitlab.com Should help.