Hi Zoltan,
I use a DDJ400, but i think the problem is not with the hardware, but with the software.
I play tech and deep house music, as well as some techno, so let's talk electronic music with very defined beats.
I have a habit of preparing my tracks "manually": I start from the grid detected by the analysis, but then, listening to the metronome, I immediately feel that it is not aligned. Then I enlarge the waveform to the maximum and intervene by moving it with the appropriate buttons. That way I'm sure the alignment is perfect and the sync works well.
This correction I have to do on about 75% of the traces because the analysis is not accurate.
It seems a very strange thing to me if you think that Rekordbox was born as a program to prepare the tracks to be played on CDJs... under this point of view Traktor was much more precise and reliable.