Overstating distance

I ran 4km side by side with my wife this evening. I wore my Fenix 6 pro , she wore her forerunner 245. My Fenix recorded the distance as 5.6k whilst her watch recorded the correct distance. The maps on Garmin connect showed equivalent routes were ran. Whilst we were running our stats were the same on our watches. It was just when we saved our runs that tge watches showed different stars for the completed runs. Any clues as to why Fenix could be so wrong. I’ve had a slew of Garmin products and this is the first time one has recorded distance wrongly