After upgrading our master to CloudBees 2.138.42.0.1, which picked up a back-ported SECURITY-534 fix, I was unable to view the server list on the Gerrit Trigger status page. The table simply read "Data Error." and the /gerrit-trigger/serverStatuses call returns a 404. The servers themselves seemed functional according to the logs. Also in the logs:

WARNING: New Stapler dispatch rules result in the URL "/gerrit-trigger/serverStatuses" no longer being allowed. If you consider it safe to use, add the following to the whitelist: "com.sonyericsson.hudson.plugins.gerrit.trigger.GerritManagement serverStatuses". Learn more: https://jenkins.io/redirect/stapler-facet-restrictions

Adding the above to the whitelist fixed the issue.