Reproduction steps:
1. Download and open project 'Multidisplayissue.zip'
2. Open Scene 'SampleScene'
3. Enter Play Mode
4. Try clicking Sphere GameObject (It should turn red if the click is registered)
5. Change Display in Game View to Display 2
6. Try clicking Sphere GameObject (It should turn red if the click is registered)
7. Change Display in Game View to Display 3 (Optional)
8. Try clicking Sphere GameObject (It should turn red if the click is registered) (Optional)

Expected result: Clicks are registered on all Displays in Game
Actual result: Clicks are registered only on one Display in Game

Reproducible with: 2018.4.32f1, 2019.4.21f1, 2020.2.6f1, 2021.1.0b8, 2021.2.0a7

Notes:
- Issue was not reproducible if Game was built with Fullscreen Mode set to Fullscreen Window
- Issue was reproduced in Windows Build, Windows and macOS Editors
- Could not test with macOS Player
- Usually, the click is detected in Display 1 but sometimes it can switch to other Displays