Inaccurate Max Speed On Strava

I use Strava when I go out on my mountain bike and I track my rides and walks using my Apple Watch SE. Until about a fortnight ago, it seemed accurate and informative and it was ace to use. Since then, the maximum speed recorded has been a million miles off. Today, for example, I rode my ebike and it has a built in reading on the display for speed, distance and so on - I know my max speed was 20mph today because I was chilling, listening to headphones and so on, but when I opened Strava it suggests I hit 36mph which is insane!

I’m getting close to a Factory Reset, because tracking my activities is what I bought my AWSE for and it’s not working properly anymore. Any suggestions from anyone? Or is anybody having the same issue?