https://github.com/jenkinsci/github-branch-source-plugin/blob/d60cc7617ee9ad56fd3ea3a3c3ad2569dc07c827/src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubSCMSource.java#L1163

the regex "^PR-(
d+)(.)?$" includes {} in the second matching group which means PR-11-HEAD will never match the strategy of HEAD as the second matching group includes the {}. Just need to do something like "^PR(
d+)(:?-(.))?$" (if I can remember my regex for non-matching groups correctly)