I am using the "Bitbucket Server Integration" plugin, with a multibranch pipeline, and I have it set to build automatically all pull requests.

We are not using https://plugins.jenkins.io/bitbucket-push-and-pull-request/ or https://plugins.jenkins.io/bitbucket-build-status-notifier/

Only https://plugins.jenkins.io/atlassian-bitbucket-server-integration/

The plugin is reporting the build status (e.g. INPROGRESS or FAILED) to the Bitbucket api for the destination branch (e.g. develop) and for the pull request branch (e.g. PR-1234), but NOT for the source branch of the pull request (e.g. feature/some-branch).

This results in the build status showing up on the Bitbucket Web UI only in certain places, and not all of the expected locations (outlined in red in attached screenshots).
Notably, builds using the same job and jenkinsfile which are not Pull Request builds do show up correctly on the list of all pull requests in the Bitbucket UI. So, this issue only affects pull requests.