Reproduction steps:
1. Open the attached “BugRepro” project
2. Click File > Build
3. Make sure that Development Build and Script Debugging is enabled
4. Click Build And Run
5. In Console Window, select the built Player as the Target
6. In Player, click the Left Mouse Button repeatedly
7. Observe the Mouse Delta Values in the Console Window

Expected result: Mouse Delta Values are (0.00, 0.00) when clicking LMB repeatedly on the Player window while the cursor is motionless
Actual result: Mouse Delta Values are random when clicking LMB repeatedly on the Player window while the cursor is motionless

Reproducible with: 2021.3.29f1, 2022.3.8f1, 2023.1.10f1, 2023.2.0b6, 2023.3.0a2

Reproducible on: Ubuntu 23.04
Not reproducible on: Windows 10 Pro 22H2, macOS 13.4.1