[Solved] Problem with slip mode

Tried Rekordbox 4 with a DDJ-SZ, if I set the Slip mode ON and do a backspin, when the backspin ends, the tracks restarts at the time the backspin ends and not at the time it should be.
It's strange because when I do the backspin, I clearly see the grey bar on the waveform moves forward, but when the track "restarts", it's not where the grey bar is.
In other words, when I do a backspin, the slip mode has no effect.
The problem occurs also randomly when using the Slip loops.