Heartrate strange behavior after release 24.12 with HRM-pro plus

Added is a picture of a registered heartrate. At 7:25, 18:34, 29:27 and 39:52 the registered heartrate stops to 0 en after that it registered the right heartrate. Nothing has changed, beside the firmware of the Forerunner. The HRM-pro plus is used for multiple months without any problem. I switched the forerunner completely off and after it i switched it on again, but this gave no solution.

Are there any ideas of the cause / what i can do to solve this?

Thanks, Gert-Jan