When using Bitbucket server as a branch source in Multibranch pipeline, the webhook is properly created and sends the payload, but Jenkins does not trigger a build.

Regular pipelines will properly trigger the build, just not multibranch pipelines.

This is outputted in the logs:
May 21, 2020 6:10:50 AM WARNING jenkins.scm.api.SCMHeadEvent$DispatcherImpl log
SCMEventListener.onSCMHeadEvent(SCMHeadEvent) jenkins.branch.MultiBranchProject$SCMEventListenerImpl@1047d05 propagated an exception java.lang.NullPointerException at hudson.Util.getDigestOf(Util.java:634) at jenkins.plugins.git.AbstractGitSCMSource.getCacheEntry(AbstractGitSCMSource.java:1376) at jenkins.plugins.git.AbstractGitSCMSource.getCacheEntry(AbstractGitSCMSource.java:1211) at jenkins.plugins.git.AbstractGitSCMSource.doRetrieve(AbstractGitSCMSource.java:339) at jenkins.plugins.git.AbstractGitSCMSource.retrieve(AbstractGitSCMSource.java:561) at com.atlassian.bitbucket.jenkins.internal.scm.BitbucketSCMSource$CustomGitSCMSource.accessibleRetrieve(BitbucketSCMSource.java:447) at com.atlassian.bitbucket.jenkins.internal.scm.BitbucketSCMSource.retrieve(BitbucketSCMSource.java:189) at jenkins.scm.api.SCMSource._retrieve(SCMSource.java:373) at jenkins.scm.api.SCMSource.fetch(SCMSource.java:327) at jenkins.branch.MultiBranchProject$SCMEventListenerImpl.processHeadUpdate(MultiBranchProject.java:1683) at jenkins.branch.MultiBranchProject$SCMEventListenerImpl.onSCMHeadEvent(MultiBranchProject.java:1192) at jenkins.scm.api.SCMHeadEvent$DispatcherImpl.fire(SCMHeadEvent.java:246) at jenkins.scm.api.SCMHeadEvent$DispatcherImpl.fire(SCMHeadEvent.java:229) at jenkins.scm.api.SCMEvent$Dispatcher.run(SCMEvent.java:505) at jenkins.security.ImpersonatingScheduledExecutorService$1.run(ImpersonatingScheduledExecutorService.java:58) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748)
May 21, 2020 6:14:59 AM INFO com.atlassian.bitbucket.jenkins.internal.http.HttpRequestExecutorImpl handleError
Bitbucket - did not accept the request
May 21, 2020 6:16:39 AM INFO com.atlassian.bitbucket.jenkins.internal.http.HttpRequestExecutorImpl handleError
Bitbucket - did not accept the request