Not an expert in this area but I believe it is the tolerance of each LED and it's transformer. I have 6 LED cans in my home theater room. They are on a dimmer. As I dim them down, 4 go out and 2 stay barely lit. I can continue to dim and they will go out also. I moved them around in the configuration so they are at the back of the room and illuminate the wet bar area. Accidentally worked out great for me! Not sure why your levels change around. Maybe try a different LED brand.