Thank you for the info! Will have to investigate this further - not able to reproduce the issue in Chrome dev tools with responsive layout testing, but one of my friends should have an iPad I can test with. So far it seems this is a Safari-specific issue.
Here is a screenshot of the problem, and my iPad model number if that helps.
https://ibb.co/d2P0X2y https://ibb.co/19qBJBz
The overlay shows in both landscape and portrait.
Hope this is helpful in some way.