So, it took me embarrassingly many shopping trips to remember to buy kefir. But I finally did. For reference, I chose Andechser Bio Kefir. But to be honest I didn't find the lid dripping. I shook before I opened and it was still fine. Repeated that a couple of times. Decided to leave some for the next day, maybe the consistency would change after opening. Still fine. Then I decided to let it warm to room temperature and still no dripping.

So unfortunately I cannot reproduce the scientific findings of @frosch.