Apple Watch Series 6 - HRV readings innacurate?

We've worn our Apple Watches now for years, and although I know that the terms specifically mention that readings are not to be used as medical direction, nor the degree of accuracy is guaranteed, I have noticed on June 2, 2023 that my HRV readings have been incredibly inaccurate. When the watch checks for AFib randomly, I've noticed my HRV numbers drop significantly. When I do a "Breathe Exercise", the HRV number is sometimes 30, 40, 50 points (or more) higher than the watches independent check of my HRV. I didn't know if this was specific to the Series 6, and 7... but perhaps it's time to invest in a Series 8? Is anyone else experiencing this? I do take Lisinopril/HCTZ twice daily, and 1/2 of a 25 mg Atenolol (Beta Blocker) in the morning, and 1/2 at night. My heart rate ranges in the mid-50's to 60's at rest, and during exacerbations, it does spike to the 120's - and this is with the Atenolol. Our Cardiologist said that HRV is a relative score, and we've done the holter monitor, EKG, Echocardiogram... He says that all is normal. My BP readings are usually 100/70. Again, I'm not sure if there was a watch update around June 2nd, but after that, my HRV readings when the watch does them randomly are incredibly different than when I use the Breath app. Again, anyone else experiencing this problem? Any guidance would be most appreciated.