I've brewed 10 batches and have had some excellent results without a lot of trouble, but with this new batch of honey weizen I came across something odd. The airlock isn't bubbling at all until I tap on the carboy. Even if I just flick it, it starts to bubble like a regular primary ferment. It's been in the carboy for 3 days and has a nice krausen on it, also I know there aren't any leaks in the airlock or bung. Can anyone explain this?