During my tests of the official latest release 7.46.0, I found another issue related to the loading screen. When the scrollbar is present and already scrolled, the loading screen (whether single or multiple) is misplaced because it doesn’t account for the scroll offset.
This is not a regression, you can verify it using the following repro sample with previous version 7.45.0:
The above sandbox is the exact copy of the example from documentation Starter HTML Template with modifications to the overflow attribute, the addition of the engine.displayLoadingUI method and the inclusion of a big container to reproduce the scrollbar behaviour.
I have created a pull request to add the missing scroll offsets:
Again, happy to consider better approaches or changes needed!