There is a”sweetspot” tension for the preload. If you overtighten, they will work loose, leave it too low tension, they will work loose. It is best done with the wheels in the frame or fork.
If I recall correctly, the best method is to lift the bike wheel off the ground, and whilst spinning the wheel slacken off the tension then tighten till you feel a resistance and the wheel starts to slow down. Then back off the tension about 1/8 turn.
However, you may have to do what I was advised to do by a Mavic dealer, which is to set the tension as above, then drop a few drops of Loctite onto outside the thread of the tension nut. Leave overnight. This stops the nut backing off and my Crossmax with a similar type of hub has been fine for nearly two years.