Traktor v2.6 and loop sample sync

Hi,

I'm having a problem with sample decks in Traktor since its beginig, despite using the Kontrol F1.
Either I'm completly dumb or something is not working as expected...

Here is what I do :

1) load a song in deck A
2) Analyze is done so the song is beat-grided automaticaly (confirm ?)
3) play the song and at some point create a 8 beats loop
4) use the Kontrol F1 to copy the loop in an empty new sample remix deck
5) get out of the loop and keep the song playing
6) trigger the sample from the sample deck and expect it to be sync-ed with the current song

Problem is the sample is not "aligned" with the song.
It IS beatgrided, as the tempo and length of the sample is the exact same 8 beat as the song, but it does not start when I would expect it to, which is the first beat of the 8 beat block of the song.

I hope my explaination is clear enough.
This is 100% reproductible with any song.
Even if I load a new song, use the cue/play button to start it of the first beat and trigger the sample at the same time, the sample only start on the 2, 3 or even 7th beat of the song....

I'm using latest traktor updates, fresh install, Snap (and Quantize) ON in Traktor and on the F1.
This is also happening without the F1, so it is really not related.

Can someone explain me what to do exactly to be able to record a sample and play it sync-ed (and I mean the sample starting on THE FIRST BEAT of the song) ?
I provided a video to Traktor support with no real answer about a year ago !!