My configure pages stopped working. The formatting is broken and the save buttons do not work. This sort of strands the administrator from being able to use the UI to manage Jenkins.
I am on 2.263 now but I was able to confirm this same problem happens in 2.264 and 2.265.
This was likely broken by https://issues.jenkins.io/browse/JENKINS-56109
I have also reported this via CloudBees CBJE internal ticket number 193134.