Rise in Moodle on iOS - can't scroll to bottom

I have a weird issue with scrolling in Moodle. I have blocks of content with a continue button at the bottom of each page. I can't get to that on an iPhone (I'm testing on a iPhone 6SE ios13 - the smallest one they still sell). In my mobile testing browser (Blisk) and on my older iPad (ios 10) it works just fine. It appears to be related to the screen space.

When I look at the course on the same device using the "share" link, it seems to work just fine. Is there a difference applied to the player when it is exported as scorm? (shouldn't think so). 

Moodle has these scorm appearance settings:

display: new window
width + height : 100%
options: untick all options
display name: untick
skip structure: always
disable preview: yes
display structure on entry page: no
display course structure in player: disabled

The content appears in a new window just fine and appears to work, but I am unable to get to the bottom of each screen - not just a few pixels either, but often whole sections won't be scrollable or accessible. See the attached screen recording.

I've tried setting Moodle to open the content in the same window rather than a popup but then the content space is so tiny on the iphone 6SE you can't even see anything. People say "that's a theming problem in your site" and walk away from you if you mention it.

Since my course navigation is in restricted, this means certain pages block the completion of the course because scrolling doesn't work. What can be done here? "Don't use iPhone" isn't a great option.