Hmmm, my phone has the same configuration as yours: Stock rom and everything. I tried what you said, recording from bright light to room & vice versa, but my transitions seem to be smooth with no lags :/ I believe your camera is on it's default settings?
When in camera mode, try panning the camera from bright light to dim & vice versa, see if there are any lags of choppiness in between the transition. If there isn't, there shouldn't be any problems. If there is, I'm not sure what's causing it.
Does anyone here has had this issue as well?