We're using a parameterized job, so that several branches of the same repo can be built concurrently. The job is configured to add a tag to the repo as a post-build action.
When we have several jobs running, they sometimes get stuck: even though a job is finished, it "waits" for the previou jobs to finish. The message is:

Git Publisher is waiting for a checkpoint on <job_name> #<prev_build_number>

This causes a chain reaction, whereby several jobs are just hanging.

I saw a similar issue in JENKINS-9913, but that seems to have been resolved, and it pertained to JUnit.