@simspi I thought my sensor was just dying, but now I’m getting suspicious…
I have a combi sensor from Coospo that is similar to yours (but crucially, no LED). Swapped the battery a week ago to be sure this wasn’t the issue.
Speed and cadence metrics seem to drop at random intervals during rides, you don’t see it while riding but can see the gaps in the FIT file afterwards.
3 days ago a 93k ride was reported as 82k despite a good gps trace - and correcting distance in Strava added the missing 11k.
2 days ago it simply wouldn’t connect at all at the start of a long ride (also about 95k); I got no apparent sign of life from it during the whole activity.
Yesterday it mysteriously connected again during a very short ride, but only displayed zero cadence throughout, and no cadence data was in the FIT file.
Now that I’ve read your message I’ll do some more testing to narrow it down, starting with using a phone app to connect the sensor.