What you ave described doesn’t sound out of the ordinary.
From my own experience I have also found that the auto-calibration feature is not particularly consistent. You can run auto-calibration twice in a row without changing the physical setup and it will give varying results. (This is probably due to the fact that the physical bulbs will behave slightly differently depending on temperature and voltage fluctuations).
My advice is to use the auto-calibrarion as a very rough guide. Experiment by manually refining Params #1 and #2 until you are happy with the behaviour for each circuit.
E.g. with some of my LED bulbs the auto-calibration will set Pram #1 (minimum brightness) to ~20%, however I have found I can reliably set it to 5% without any problems (giving a much better dimming range).