I don't think wrist side matters. Readings are not always accurate (regardless of device) the best option is to run composition tests regular at the same time each day and take average reading over a week, over a month etc. and don't take any single reading as true picture (again, regardless of device)
When I do the tests (Scales and Watch at one after the other) eg on readings watch shows Skeletal Muscle as 20 and Body fat as 40, but the Scales would show Skeletal Muscle as 40 and Body Fat as 20 (+/- 1 or 2 %)... it is not a little out!!!