Yeast does this if they are in really sweet spot for sugar, nitrogen, microelements, temperature, and pH. Almost always happens in braggot (once shot into ceiling with lock, was quite a mess), also if you add yeast fertilizer. I think I saw this reported reproducively for slightly over 23C lager yeast. And, well, insufficient headspace might be a problem. Don’t worry, at least yet.
Then it’s effectively braggot. Embrace the froth, you are cookin!