"SendMessage cannot be called during Awake, CheckConsistency, or OnValidate"

[MattTree]

This was my experience on Windows 10, Unity 2019.4.1f1, HDRP 7.4.1:

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Error message in text:

SendMessage cannot be called during Awake, CheckConsistency, or OnValidate
UnityEditor.SceneManagement.EditorSceneManager:RestoreSceneManagerSetup(SceneSetup[])
GameplayIngredients.Editor.EditorSceneSetup:RestoreSetup(EditorSceneSetup) (at LocalPackages/net.peeweek.gameplay-ingredients/Editor/EditorSceneSetup/EditorSceneSetup.cs:99)
GameplayIngredients.Editor.DiscoverWindow:LoadSceneSetup(EditorSceneSetup) (at LocalPackages/net.peeweek.gameplay-ingredients/Editor/Discover/DiscoverWindow.cs:490)
GameplayIngredients.Editor.DiscoverWindow:GlobalContentGUI() (at LocalPackages/net.peeweek.gameplay-ingredients/Editor/Discover/DiscoverWindow.cs:340)
GameplayIngredients.Editor.DiscoverWindow:OnGUI() (at LocalPackages/net.peeweek.gameplay-ingredients/Editor/Discover/DiscoverWindow.cs:274)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

[MattTree]

I looked for "SendMessage" in the mentioned files but found nothing:

[MattTree]

When I double click on the error message, HDAdditionalLightData.cs opens, though it's not mentioned in the error text:

No "SendMessage" in this file either:

[MattTree]

More exploring:

Error text:

ArgumentException: The Object you want to instantiate is null. UnityEngine.Object.CheckNullArgument (System.Object arg, System.String message) (at <3dc54541a2574ac7826a004a212a4332>:0) UnityEngine.Object.Instantiate[T] (T original) (at <3dc54541a2574ac7826a004a212a4332>:0) SamplePlayFromHere.PlayFromHere_OnPlayFromHere (UnityEngine.Vector3 position, UnityEngine.Vector3 forward) (at Assets/Scripts/GameplayIngredients/Editor/SamplePlayFromHere.cs:17) GameplayIngredients.Editor.PlayFromHere.OnEnterPlayMode (UnityEditor.PlayModeStateChange state) (at LocalPackages/net.peeweek.gameplay-ingredients/Editor/PlayFromHere.cs:79) UnityEditor.EditorApplication.Internal_PlayModeStateChanged (UnityEditor.PlayModeStateChange state) (at <a0a9ad37e16b4f7cb955e1101b72d4cc>:0)