FIX: InputActionReference when using FEPM (ISX-1968)

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -24,6 +24,7 @@ however, it has to be formatted properly to pass verification tests.
 - Fixed an issue where `InputActionAsset.FindAction(string, bool)` would throw `System.NullReferenceException` instead of returning `null` if searching for a non-existent action with an explicit action path and using `throwIfNotFound: false`, e.g. searching for "Map/Action" when `InputActionMap` "Map" exists but no `InputAction` named "Action" exists within that map [ISXB-895](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-895).
 - Fixed an issue where adding a `OnScreenButton` or `OnScreenStick` to a regular GameObject would lead to exception in editor.
 - Fixed an issue where adding a `OnScreenStick` to a regular GameObject and entering play-mode would lead to exceptions being generated.
+- Fixed InputActionReference issues when domain reloads are disabled [ISXB-601](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-601), [ISXB-718](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-718), [ISXB-900](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-900)
 
 ### Added
 - Added additional device information when logging the error due to exceeding the maximum number of events processed

Packages/com.unity.inputsystem/InputSystem/Actions/InputActionReference.cs

@@ -199,6 +199,24 @@ public static InputActionReference Create(InputAction action)
             return reference;
         }
 
+        /// <summary>
+        /// Clears the cached <see cref="m_Action"/> field for all current <see cref="InputActionReference"/> objects.
+        /// </summary>
+        /// <remarks>
+        /// After calling this, the next call to <see cref="action"/> will retrieve a new <see cref="InputAction"/> reference from the existing <see cref="InputActionAsset"/> just as if
+        /// using it for the first time. The serialized <see cref="m_Asset"/> and <see cref="m_ActionId"/> fields are not touched and will continue to hold their current values.
+        ///
+        /// This method is used to clear the Action references when exiting PlayMode since those objects are no longer valid.
+        /// </remarks>
+        internal static void ResetCachedAction()
+        {
+            var allActionRefs = Resources.FindObjectsOfTypeAll(typeof(InputActionReference));
+            foreach (InputActionReference obj in allActionRefs)
+            {
+                obj.m_Action = null;
+            }
+        }
+
         [SerializeField] internal InputActionAsset m_Asset;
         // Can't serialize System.Guid and Unity's GUID is editor only so these
         // go out as strings.

Packages/com.unity.inputsystem/InputSystem/InputSystem.cs

@@ -3662,6 +3662,9 @@ internal static void OnPlayModeChange(PlayModeStateChange change)
                     // Nuke all InputActionMapStates. Releases their unmanaged memory.
                     InputActionState.DestroyAllActionMapStates();
 
+                    // Clear the Action reference from all InputActionReference objects
+                    InputActionReference.ResetCachedAction();
+
                     // Restore settings.
                     if (!string.IsNullOrEmpty(s_SystemObject.settings))
                     {