Bump up the wattage. Remember this is only going to be the initial wattage to get the coil up to the selected temp. As soon as it gets to the right temp the wattage will then be auto-adjusted to maintain that temp. Try 25-30 watts.
So I upped the wattage to 25W and dropped the temp to 400F. mod is almost instantly going into temp protection. Smooth, steady vape.
Might play with temp settings a little, just to find the proverbial "sweet spot".