Everytime I try to calibrate the Gimball, it stops at 56% and says 'calibration fails' and ot's always the same. The movement of the camera doesn't work as well as before.

Did the drone crash , or did it fall from table or something?
Is this shortly after update of software?

Check the position of 3 tabs to hold gimbal in place
Reset camera settings, try to calibrate again.
If needed just contact DJI for support

Please refer to Anoniem's reply, please help to confirm if the drone crash or has any impact damage before. Keep us updated if the issue persists.

DJI Thor Posted at 2017-11-19 20:15
Please refer to Anoniem's reply, please help to confirm if the drone crash or has any impact damage before. Keep us updated if the issue persists.

Yes, the drone had crashed

Javier Moro Posted at 2017-11-21 05:09
Yes, the drone had crashed

How about after following Anoniem's suggestion? We highly suggest sending the drone in for an overall check of the issue persists. https://repair.dji.com/en/SelfRepair/Area