Airlock bubbling and fermentation are not the same thing. You have to separate that from your mindset. Airlock bubbling can be a sign of fermentation, but not a good one, because the airlock will often blip or not blip for various other reasons...so it is a tenuous connection at best.
If your airlock was bubbling and stopped---It doesn't mean fermentation has stopped.
If you airlock isn't bubbling, it doesn't mean your fermentation hasn't started....
If your airlock starts bubbling, it really doesn't matter.
If your airlock NEVER bubbles, it doesn't mean anything is wrong or right.
Your airlock is not a fermentation gauge, it is a VALVE to release excess co2. If it bubbles it is because it needs to, if it doesn't, it just means it doesn't need too...
Often an airlock will bubble if the fermenter has been disturbed in some way, like a change in temperature, change in atmospheric pressure, the cat brushing against it, opening it up to take a hydro reading, or in your case it could simply be offgassing because you moved it to secondary.
The co2 has sat in stasis for a period of time, then it was disturbed so it is not longer at equilibrium with everything else now. And therefore it is blipping in your airlock...
Or you could indeed have fermentation happening, since maybe your fermentation was laggy and racking it over restarted fermentation.
Airlock bubbling only tells you that co2 is coming out of the airlock, it is not telling you why. And there's various reasons. That's why it's not a good idea to equate airlock bubbling with fermentation...It could be because it is fermenting, or it could not be because of fermentation...so it's not a trustworthy tool.
Either way I wouldn't worry about it.
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