Upon release of a new version of getyourrefund which switched to a new version (6.1.x) of Ruby on Rails, the database suddenly came under more load, at which point the website was slow or unusable. After restarting the database, it was able to handle the load. This resolved the immediate issue.
The following day, we switched back to the version of Rails we were using before the upgrade.
This issue was opened retrospectively and has been resolved.