XC70 – AWD jerks, no four wheel on DSTC??

Hello forum! I had completely new experiences in the snow the days with my XC70 – is that normal? With switched off DSTC I want a steep climb up (snow depth approx. 20cm). If I want to really run through it and the traction decreases the car starts to stutter. Certainly as if the brakes on all four wheels “Rückelsig” intervene, the whole car shakes it through there…??? Furthermore, I have the phenomenon that it affects me on mountains with snow covered road and The front wheels go crazy, the rear wheels don’t go along. Only when I press reset and the DSTC kicks out it takes a second and it snaps in the Haldex and I also have traction at the rear. However, at higher speeds on normal road everything seems to work reasonably well. Is there not the possibility for some people to use the DSTC? A kind of all-wheel tuning? Greeting, maze940