I've created a pipeline multibranch project with mercurial repo as a source, build configuration set in Jenkinsfile in repo and set to build periodically to poll the repo every two minutes (H/2). The first step inside Jenkinsfile is checkout scm.

It seems that for newly created branches (that have only one commit) the changes view is totally empty. On the other hand, when there are more commits it seems that they are logged twice (see screenshot below).

This looks like a similar issue to JENKINS-30491 or JENKINS-31079 yet this time it happens with mercurial instead of git.