Create folder, then another inside (just for fun), then create a pipeline (we have multibranch pipeline) inside. Open a pipeline and you will see in address bar a URL like: "https://jenkins.magic-host.com/blue/organizations/jenkins/Company%2FBuild%2Frepo/activity"

This is a valid URL and it is possible to open activity page directly. But when you hit refresh (at least in Firefox) - all these escaped chars like "%2F" will become converted to slashes and you will get 404 error message from BlueOcean.