Apple Watch Series 9 Quits Measuring HR During Exercise

I got an Apple watch series 9 back in August 2024 to replace my series 6. Since I have had it I have noticed that is does a very poor job measuring heart rate during exercise compared to my series 6. It consistently stops measuring my hr even when the band is on snug but not too tight, and nothing else is interfering anymore than with the series 6. The series 6 would have gaps in hr measures but these were much shorter and infrequent. It is basically every time I exercise that this watch will have frequent pauses in measuring hr or it will only measure right at the beginning of an exercise and at the very end. It does this for all types of exercise too, walking, running, skiing, skating, core training etc. I have reset it, recalibrated it, and still it continues to stop measuring hr throughout my exercises.

Other than this I love my watch!