Repro steps:
1. Open the user's attached project "Sidestep.zip"
2. Open the scene Assets > Scenes > MainMenu
3. Plug in two Xbox One controllers and remember which one was plugged in first
4. Enter Play Mode
5. Press "A" on the second connected controller to join the game

Expected result: A new player joins the game
Actual result: A new player doesn't join the game

Reproducible with:
- 2019.3.0a2 (Input System preview.6 - 1.0.0),
- 2019.3.6f1 (Input System preview.5 - 1.0.0),
- 2020.1.0a1 (Input System preview.6 - 1.0.0),
- 2020.1.0b2 (Input System preview.6 - 1.0.0),
- 2020.2.0a2 (Input System preview.5 - 1.0.0),
- 2020.2.0a3 (Input System preview.5 - 1.0.0)
Not reproducible with: 2019.3.6f1 (Input System preview - 0.9.1), 2019.3.6f1 (Input System preview.4 - 1.0.0)
Could not test with: 2017.4 due to Input System package being unavailable, 2018.4, 2019.3.0a1, 2020.2.0a1 due to errors

Notes:
- If another player joins the game using the controller that was plugged in first, the other one is allowed to join as well
- PlayerInputManager component is used to handle local co-op