Swipe to next chapter when in vertical scroll mode sometimes lands between pages

[sstennis1]

Describe the bug

In the iOS Test App with vertical scroll mode enabled, if you quickly swipe back and forth (left and right) in an epub reflowable book sometimes the current page and the next page are both visible on the screen when scrolling is done. This is not easily reproducible and an edge case, of course, but thought you might like to know anyway.

How to reproduce?

1. Launch the iOS Test App on iPhone hardware
2. Open an epub reflowable book (e.g.: Jane Eyre - available from the OPDS feed)
3. Move a few chapters into the book
4. Swipe left and right quickly back and forth

Readium version

3.5.0

OS version

ios 26.1

Testing device

iPhone 16 Pro

Environment

macOS: 15.6
platform: arm64
Xcode 26.1.1
Build version 17B100

Additional context