Why doesn't Apple Watch7 track workout accurately?

I just took my bike around town to run errands, and during the course of my trip, saw that the watch was keeping accurate track of my time and distance, and had gone beyond the time for the exercise ring to close. Later, when I had been home for a while, I saw that my watch face had gone "blank", and I had to use the passcode to get back into it. When I did, the exercise ring is not closed, and the entire time for my workout has been changed to less time than the actual.

How can I fix this issue? I recently did a reset, but have not gone as far as unpairing and re-pairing.