Apple watch heart rate not being tracked

I was doing a bike race the other day and i started and paused my workout before the race started and once the race started i resumed my workout but i didn't get any heart rate data. i tried opening the heart rate app and it just couldn't record the heart rate. Then the other day i did another ride and it was fine with the heart rate tracking and stopped when it was paused but on my way home the heart rate data stopped being tracked i attached images to show whats happening. It's like the heart rate data is fine then just stops. For reference i am using a Apple Watch Series 8 which i have had since 25th december 2022 and it has been happening for about 2-3 months the heart rate data issue every now and then