My primary bucket almost never bubbles through the airlock, but I haven't had a bad brew yet.
Airlock bubbling is no indicator of fermentation activity, so don't worry too much about it. As long as your hydrometer readings show activity, you're fine.
That happened to me once because i didn't have a good seal with the rubber gasket around the airlock. Make sure it's snug and make sure the lid is totally on all the way around.