I have a GIT Branch called "v10/release".
1. In default UI of Jenkins, the link of this branch in my "ice" Github repository (/job/ice/) is : "/job/ice/job/v10%252Frelease/" (404 error) instead of "/job/ice/job/v10%2Frelease/" which works (display correctly the page, I can execute a build, see logs, etc...)
note: All branches without slashes work perfectly.
2. In Blue Ocean, Jobs of this branch are listed, but not displayed correctly:
As you can see in my screenshot, urls are also double encoded