When using the "Prevent multiple jobs with identical parameters from running concurrently" feature, concurrent jobs are only allowed after going into each job's configure page, then clicking save on them. Restarting jenkins reverts back to the behavior of not allowing concurrent jobs, and once again going back into each job's configuration page and clicking save re-enables concurrent jobs.

The settings on the jobs are:
ghprbPullAuthorLogin (string parameter)
ghprbSourceBranch (string parameter)
... lots of other parameters
Throttle concurrent builds (checked)
Throttle this project alone
Maximum total concurrent builds: 10
Maximum concurrent builds per node: 10
Prevent multiple jobs with identical parameters from running concurrently (checked)
List of parameters to check: ghprbPullAuthorLogin, ghprbSourceBranch

This functionality is really critical for us, and this bug makes this plugin barely usable.