Vertical scroll bar is missing after upgrade to Universal Theme

I'm using Oracle 18.c and Apex 19.1. I recently switched an existing application to Universal Theme. I noticed that the vertical scrolls were missing from interactive reports and from forms. I was able to restore the vertical and horizontal scrolls to the Interactive Report by going to Attributes / Heading. I set the Fixed To = Region and set the Maximum Report Height to 680. That seems to have fixed the problem with Interactive Reports.

However I still have a problem with Forms. While editing the page in Apex, I click on the form name, and note that the Appearance / Template is set to Standard and the Appearance / Template Options is set to Use Template Defaults, Scroll - Default. I can't figure out how to enable the vertical scroll so that users can edit fields on the lower part of the form.

I should add that there is indeed a scroll bar on the form. The scroll bar itself slides up and down, but the body of the screen remains still.