Hello. Author. There is a bug I'd look to report. I've only discovered this when struggling with the Hardcore level but after dying reportedly; I can't hit the restart button with the controller with a direct A. That is to say the button wasn't automatically selected. It was still clickable with a mouse however. And it was only one in a couple losses too, not constantly.
I actually think I already have the answer. Whenever you open up the restart panel you can call "EventSystem.current.SetSelectedGameObject(restartButtonGameObjectName);". This should in theory make the restart button automatically selected.
Source: https://stackoverflow.com/questions/73923902/how-to-select-an-object-by-script-u...
https://docs.unity3d.com/Packages/com.unity.ugui@2.0/api/UnityEngine.EventSystem...