Reproduction steps:
1. Open the attached user's project "NewUI.zip"
2. Build for Standalone Player
3. Click on the pink panel
4. Check the Player.log

Expected result: PointerDownEvent reports mouse button presses with "pressed=1", "pressed=2" or "pressed=4"
Actual result: PointerDownEvent reports mouse button presses with "pressed=0" in the Player.log

Reproduces on: 2021.2.15f1
Does not reproduce on: 2022.1.0b11, 2022.2.0a9
Could not test 2019.4.36f1, 2020.3.32f1 due to package errors when downgrading

Notes:
-Issue does not reproduce in the Editor