I am experiencing weird behavior with the Pages feature of GitLab Omnibus package running on an Ubuntu 16.04 virtual machine. Some projects use Pages with Jekyll built by GitLab CI, which has been working as expected since it was first published with Gitlab CE.
For a couple of days now, visiting any of the homepages of those sites shows the content of just one of the projects. Each of them should of course show different content, but they all show the same. Even stranger: the content shown on each of the sites changes over time to one of the other projects, and I can not see whether this is deterministic.
Restarting the build processes of each of the projects did not fix this, neither did gitlab-ctl reconfigure, stop and start, nor rebooting the entire VM.
To investigate on that issue, I edited (which I assume is) the resulting file of the build process at /var/opt/gitlab/gitlab-rails/shared/pages/www/www.domain.org/public/index.html. Not in the first place, but later on during the already stated "rotating" content, the edits showed up on the webpage.
So what is going on there? Is this some caching issue? Is it malconfiguration? Is it a bug? Please help me find and fix the problem, as those are production websites.