We have used jenkins for a while successfully, but now we are facing a issue, we cannot handle anymore ourself. Also the Jenkins takes roughly 10 minutes to load now the pages. So we are nearly lost now with the jenkins...

basically I am getting similar issues like this (see the attached logfile)
WARNING: Caught exception evaluating: it.getJaCoCoCoverageResultSummary(jobs) in /jenkins/. Reason: java.lang.ClassCastException: com.cloudbees.hudson.plugins.folder.Folder cannot be cast to hudson.model.Job
java.lang.ClassCastException: com.cloudbees.hudson.plugins.folder.Folder cannot be cast to hudson.model.Job

Hope someone can provide us a workaround?