When a mouse scroll is started in one widget e.g. QListWidget and before the scrolling ends moving the mouse cursor over another widget the scrolling continues there.
Use the attached test application to reproduce the issue.
1. Launch the app
2. Start the mouse scroll on the left QListWidget and immediately move mouse cursor over the other QListWidget on the right
The issue can be reproduced with Apple Magic Mouse and not with the Magic Trackpad.