If "build current patchset only" is enabled and the system issues a cancel to a job that is currently fetching from gerrit, the locks are not cleared on the workspace. The next job to run on that workspace will fail as it detects the previous fetch is still in progress.
We see this when a developer uploads two patchsets within a minute of each other, and the gerrit fetch operation takes 3+ minutes.
Workaround is to disable the feature.
The Cancel operation should reset any active locks.