Series 3 watch GPS tracking inaccurate data

Hi, I have happily been using the workout app to track my runs on my series 3 watch for 4 years. However in the last 3 months the tracking has been vastly inaccurate on distance. This weekend I ran a 5k with a friend,’who was also using a series 3 Apple Watch and my watch tracked 0.5 mile shorter that hers.

On a 3 mile run that is huge.

I’ve checked the motion and locator services are on, I’ve tests the watch, the software updates are up to date. Has anyone seen this or got ideas on how to fix it?

I fear I may be ditching this watch a buying a Garmin soon 😬. Thanks!