Build status stuck at pending

I haven’t checked every single project, but on the 3 I did check, my builds are getting stuck in “pending” status. The build page shows no output from the job. Just a black rectangle with the loading gif.

I spent a couple hours Googling. The only things I found that seem possible were removing the directories in /var/opt/gitlab/gitlab-ci/builds and /home/gitlab_ci_multi_runner/builds. It did not help.

I have no idea what log file to watch for any clues on what is going on…

I did upgrade to the latest release today. As well as restart the VM.

This is a self-hosted Omnibus CE instance on Ubuntu 14.04.

Any suggestions?