After upgrading from Jenkins 2.32.3 with Gerrit Trigger Plugin 2.23.0 to Jenkins 2.60.3 with Gerrit Trigger Plugin 2.25.0, jobs are usually triggered as expected when checkins come in for review.  When a very large merge commit comes in, the Gerrit trigger doesn't trigger a build (either by noticing the event for the creation of the patchset, or a comment matching a regular expression).  Most of the time, a job gets triggered, just not for very large merge commits.

In looking at other bugs, JENKINS-44568 looked the most likely to be relevant, but we're seeing this on 2.25.0 which is supposed to have the fix for JENKINS-44568.  If the fix for that was to increase a buffer size as some of the discussion suggested, then perhaps our use is producing even larger messages than that fix accommodates.  If there's a way to measure this, I'd be happy to provide more data.