This issue still exists in the latest Jenkins version. I found a newer yet less voted bug with "kind of" workaround by Tsvi Mostovicz: https://issues.jenkins-ci.org/browse/JENKINS-38608?focusedCommentId=328089&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-328089
I can confirm that this issue appears when I added new 4 string parameters to the task. The last parameter was a label parameter.