Incorrect mileage on Apple Watch 4

The watch has been recording my mileage way off. It used to be slightly off, which I saw, for example, when I took a walk that has mileage marked. I’d previously checked the mileage of that particular walk with other mileage trackers. The other trackers were always slightly higher, which made sense, since I never walked perfectly straight along the route. The Apple Watch was always a little lower - for example, the walk is 6.4 miles long. My watch would show it at maybe 5.9 miles. I wasn’t happy, but it was close-ish.

But, now I don’t know what happened. It’s marking the mileage wildly off. It shows me walking over 10 miles, when I walked a little over 3 miles. The weird thing is, the steps are pretty close, at around 8,000. Then I checked for yesterday. It says I walked more than 13 miles, but I walked about 6 miles. Again, the steps are a lot closer, or more accurate. I’m not sure if the watch is double counting, or what?

The altitude is also off.

I’m beginning to think I made a huge mistake getting the Apple Watch, and maybe should have stayed with Fitbit, which was more accurate.