RAW IMU Data stops logging on wrist down

Hello,

I'm having a problem on my watchOS app where even though I have instantiated a WKExtendedRuntimeSession the app stops logging IMU data a few seconds after the watch has gone to sleep.

This happens on my Apple Watch Series 6, but does not happen on the latest Apple Watch Series 8. CPU usage in both cases does not exceed 70%, so I doubt my app is exceeding the limits thus cancelling the WKExtendedRuntimeSession. To back that up, I am not getting the WKExtendedRuntimeSessionInvalidationReason trigger I was suggested to put in place form the documentation.

I have tested a couple of different sample rates, this does not seem to happen with a sample rate as low as 1, but does happen already with a sample rate of 30.

Could it be a watch limitation, or am I forgetting something?

P.S. I have also set the background mode to physical therapy and ticket the workout processing box.