Garmin Venu not measuring heart rate accurately

I just finished a 4 round workout of 500 meter row, 25 kettlebell swings, and 10 Devil press. My Garmin recorded my heart rate at the end of this workout at 26 BPM. That is in no way accurate as I was near death at end of last round. This is the second time where this device has not recorded my heart rate accurately. It’s also the second time I’ve worked out with it. Ready to return this and go back to Whoop. What’s the issue with this device?