Reply to Freeze when loading a track

Hey,

I've got kontrol S4 with last update. A thing happens every time i load a track in deck A o B : wave-form takes long time to come and it freezes a bit. Sound continues but sometimes it takes long to see my next track !

What can i do ?

Secondly, each time native intruments makes an update, i must apply it ? I see traktor pro 2.5 is for their new controller but i haven't it. Update or not ?