How to reproduce:
1. Open user's attached project using the EnvIronman VM (more information in Edit)
2. Load GYM_INPUT_01 scene
3. Enter the play mode
4. Use WASD keys for input
Notice errors in a console. If the error doesn't appear, select other editor windows, such as Scene.

Expected result: Inputs work without errors.
Actual result: Errors appear:
Missing Profiler.EndSample (BeginSample and EndSample count must match): InputCheckForUnpairedDeviceActivity
Previous 5 samples:
onBeforeUpdate
InputCheckForUnpairedDeviceActivity
UnityEngine.InputModule.dll!UnityEngineInternal.Input::NativeInputSystem.NotifyBeforeUpdate()
UnityEngine.InputModule.dll!UnityEngineInternal.Input::NativeInputSystem.ShouldRunUpdate()
Titanium.Input.dll!Titanium.Input::FixedTimeStepInputHack.FixedUpdate()
In the scope:
InputCheckForUnpairedDeviceActivity
UnityEngine.InputModule.dll!UnityEngineInternal.Input::NativeInputSystem.NotifyBeforeUpdate()
Titanium.Input.dll!Titanium.Input::FixedTimeStepInputHack.FixedUpdate()
FixedBehaviourUpdate
FixedUpdate.ScriptRunBehaviourFixedUpdate

Reproduced with: 2019.3.0a12.
Reproduced on Package: Input System 0.9.1, 0.9.2.
Regression introduced in between 2019.3.0a9 - 2019.3.0a11 versions of Unity.

Notes:
Can be reproduced only on 2019.3 version of Unity. Other versions open with errors.
Can't be tested on 0.2.0 - 0.9.0 versions of the Input System package. Updating to any of these versions leads to errors.
User mentioned that this issue happened after upgrading from 2019.3.0a8 to 2019.3.0a11 version of Unity. Can't test on 2019.3.0a8 version because of errors on opening.