Or it could be reception? I have a Garmin computer for my bike, and it was set to monitor the GPS signal nearly constantly, and the signal would drop a lot, and the unit would freak out and lose its speed and distance accuracy to the point of posting outrageous speeds and GPS positioning. Garmin had to fix that with a software update, and I also was able to adjust the sample times. Apple doesn't allow that kind of adjustment, but I was wondering if some of what you might be experiencing is that effect, when the watch loses the signal. Not much can be done if that's what is happening except live with it until they decide to fix it. I wonder if there is anything in the AW logs, if you can find them, and sift through them, but since you are saying it's not happening anymore, it's a moot point.
Ahh the joys of high technology...