You could be kegging too early and ending up with a bit of a yeast cake at the bottom of the keg. So when you pour a glass, there is a momentary drop in gas pressure causing the sediment to rise, much like opening a bottle when the yeast sediment starts to rise as the brew fizzes up.
The beer in most of the keg could be crystal clear but if there is too much sediment you could be picking up some with every glass.
Are you able to cold condition the beer for a few more days before kegging? This should solve the problem. It's unlikely to be chill haze which is not a feature of kit brews. Otherwise as suggested, use gelatine finings but avoid knocking the keg as gelatine settles the beer well but can "fluff up" the sediment if disturbed.