I'm experiencing the same problem, and interestingly, for about the same period as you, about 3 months.

Samsung support in Brazil informed me that when the smartwatch enters what I call "power saving mode" (I'm not sure if that's the correct term), the sensor sends information to the registered listeners in batches every 10 minutes, but I couldn't pinpoint this. My listener simply stops receiving data.

I'm struggling to solve this. If I succeed, I'll post here so you know.

Good luck!!!