Issues with instantiating prefabs

Hello, 

I have encountered multiple times different issues when instantiating prefabs (via standard GameObject.Instantiate or Addressables), 

Since my scene is data-driven, I am loading most of my Game Objects on Awake() / Start(), and that causes a real mess - 

The environment which is loaded using GameObject.Instantiate() has no materials/textures, it is completely black.

The NPC I am instantiating (also by using GameObject.Instantiate()) is not loaded at all as far as I can tell. 

One more thing I encountered when instantiating via addressables, is that the player input actions are disabled (but it works well with GameObject.Instantiate()).

It goes without saying that it works perfectly fine on my desktop when running it in the editor.

What could possibly go wrong here and I can I fix that..?

Thank you in advance