Hi
I have had this to, it started when I accidently analysed a few tracks dynamically, when I removed them from my collection and re-added and analysed normally it stopped.
I also had a similar problem when I used mixed in key to sort out a few tracks, when then adding them to an SD card or USB stick I had some very strange speeding up and slowing down.
This can get to be quite a problem when you are in the middle of a mix and you have the track in time and it very slowly speeds up or slows down.
Would be interested if anyone else has had the same, I'm also using Cdj2000NXS2's and DJM750Mk2 mixer.
Any help appreciated..