Steps to reproduce:
1. Open attached project.
2. Start play mode
3. Press "B" (menu window will pop up)
4. Select Items (Items list will pop up on the right side)
5. Move mouse over items list and try to scroll up or down (do not move mouse)
- scrolling stops shortly

NOTE: Only reproducible when the mouse is not moving when scrolling.

Where to find "Items list" gameObject with scroll rect attached:
1. Pause play mode
2. mainGameCanvas->gameMenu->itemsSection->categoryItemsList.

Current result: Scroll rect stops scrolling after rotating mouse wheel a bit.
Expected result: Scroll rect should detect Input even when the mouse is not moving.

Reproduced on: 5.5.0b1, 5.4.0p2, 5.3.6f1

5.2.3p3 throws errors.