Pipelines can have stages named with a question mark inside, but if that stage has an input step (with 'parameters' so that it brings up the input in a hyperlinked page) the question mark breaks the input return URI.  You get a 404 when you click the hyperlink in the input dialog.

To repro:

Put this stage into a pipeline

      stage('Approve?')
      {
            input {
                message "Should we continue?"
                ok "Yes, we should."
                parameters {
                    string(name: 'PERSON', defaultValue: 'Mr Jenkins', description: 'Who should I say hello to?')
                }
            }
            steps {
                echo "Hello, ${PERSON}, nice to meet you."
            }
      }

During pipeline execution, when coming to input step, it blocks in the console on a hyperlink "Input requested".  Clicking the hyperlink takes you to the input dialog.  Trying to click Ok gives a 404 since the stage name is in the URI.