Apple watch series 3 distance tracking

My wife and I walk together and she and I get different mileages on the same walk. There is always about 0.3 mile-0.5 mile difference in the distance that we completed. We start from the same position side by side, and start the outdoor app at the same time. By the end of walk there is always a distance difference. Her watch (Series 1) is always showing more distance than mine (Series 3, without cellular).

We both have done the following:

• Check that Location Services (the main setting at the top) is turned on.
• In the list of apps beneath, check that Apple Watch Workout is set to While Using.
• Also enable options under System Services including Motion Calibration & Distance, Wi-Fi Networking and Mobile Network Search.
• In the Watch app, go to: My Watch (tab) > Health > Edit - tap and adjust items, then tap on Done.

However we still have the same or similar distance issues.

Anyone with other suggestions?

thanks in advance