Frontflips spin way faster than backflips (BUG)?

[L'Arçonneur]

On big jumps, I can do double/triple/quadruple frontflips with bigspins super easily and constantly without any problem, but I can barely do one single backflip on the same jump. I tried to change the timing, but I just can't do it. I thought it was intentend, but now I'm at the Markus Cleveland mission and the task is to do a triple cork so im stuck... I guess I would assume I'm the problem if frontflips also didn't work, but they do : frontflip rotations perfectly work!!! I can do quadruple frontflips and not a single double backflips... I'm completly stuck :(