I don't have a lot of experience yet with the clips but have had a couple of times that I stopped and forgot to unclip, thank goodness for some good balance, but I did find that when I panicked and pulled straight up my shoe came lose, thanks to very lose clips! that is definately something you should check.

I watched several people in a group ride, most only unclipped one foot, one fellow did both each time and seemed very unsteady when he stopped

If you can use a trainer do so, I started with mine there and clipped and unclipped a lot to get used to it.

good luck!