When prompted to confirm changing the name of a job ("Are you sure about renaming ...?"), after selecting "Yes":
(1) Loading of the next page never completes. The page identified above remains, with the loading icon in the browser just spinning endlessly.
(2) After a while Jenkins will be unreachable. In this state, running "service jenkins status" can sometimes report 2 Jenkins instances running (!!!). Restarting the Jenkins process solves the issue.
Nothing unusual in the logs.
Given that this is present in both versions specified above, I suspect this may be due to a plugin. How can I go about trying to debug this? Note that this is a production system.