OW swim and GPS accuracy

The Fenix  7xs is accompanying me for almost 2 months, I do running, swimming, and biking with it. Pool swimming was without problems so far. I started OW swimming 2 days ago, and it seem to work somehow. The watch recorded a track I swam, but distance was almost 200 m too low, as I found out by exporting the track as a gpx file and reloaded back to Garmin connect. It seem, as if the watch does record gps points correct but somehow mix up numbers in the header: (record 1305m, correct would be 1530 m). Today I swam another round with a comparable path, and this time the track was completely mixed, giving sort of a fantasy path. Swimming distance was slightly longer, close to 2000m.

With respect to GPS track recording and distance calculating: Running as well as biking show similar ‚low-distance-recording‘ of about 2%, which apparently has nothing to do with hardware recording in the watch. This ‚error’ was observed also for previous models. Why, Garmin, can‘t you get the most important thing not correct, which just seem to be a software issue?