This issue is a consequence of another one which I described in the ticket https://issues.jenkins-ci.org/browse/JENKINS-61217.

The problem is when one runs a new build the stage view is displaying only one row with the stages for the currently running build. It happens most probably because somebody programmed the plugin in such a way that stages for previous builds are removed (or just are not displayed) if they don't match stages for the last build.
When the running build finishes and the plugin makes sure that the stages were not changed they are displayed again, otherwise (if they changed) only the row for the last build is displayed.

Expected behaviour (what I propose): The stage view for previous builds should be untouched until the currently running build completes. The stage view for previous builds should be displayed independently on the currently running build (as a separate picture). And only when the current build completes - only then we should make a decision what to do with the previous ones (remove from the picture or not).