When we have more than 1 set of credentials configured in "Jenkins > Manage Jenkins > Configure System > GitHub Pull Request Builder," all jobs using the GitHub Pull Request Builder plugin default to using the first set of configured credentials – regardless of which set of credentials is selected during job configuration and save.

To clarify, if we have configured 2 sets of credentials in the global configuration of the plugin, we can modify a job using the plugin to use the second set of credentials and save that configuration... but the configuration does not persist into the config.xml, and the first set of credentials will be used instead and will be shown as selected in the job configuration.