The rule which modified to fix the behavior in Pega 7.1.6 is pzPega_UI_events.js. As there are mobile feature added to the product, there is huge difference in the code between the versions Pega 7.1.6 and Pega 7.1.9. Hence, there is no direct hotfix available in Pega 7.1.9 for the issue.
As you have already raised SR, you will get assistance from GCS to fix the behaviour
Please feel free to comment if you have questions in this regard.