Usually, it is because the bottom end point is set too low. Please readjust the top and bottom end points and make sure that the drive stops as soon as the gate is closed. If necessary, release the button a little earlier during the adjustment and slowly feel your way to the suitable end point.
You also have the option of activating the so-called Back Jump function, which reverses briefly after the gate closes in order to relieve the belt somewhat.
It may be necessary to retighten the belt slightly. In any case, unlock the door by activating the emergency release before you tighten the belt to achieve an even tension.