The plus symbol '+' (in the branch name "branchNameWithPlus") is not URL-encoded as it should be '%2B' for the following branch link URL in Blue Ocean (v1.25.4):

https://{jenkins_host_name}/blue/organizations/jenkins/{jobPath}/activity?branch={branchNameWithPlus}

It's possible to see, as expected, the page at

https://{jenkins_host_name}/blue/organizations/jenkins/{jobPath}/detail/{branchNameWithPlus}/{buildNumber}/pipeline

however, if you click on the branch link on that page, it looks like the branch name is partially encoded because any slash '/' is converted into '%2F', but the plus '+' is not, and it is replaced with a space ' ' from the string value on the page where the message