chances are that the clips on the X5 are giving in... they are THE weakest link in the window setup. limiting the travel will not help, the motors operate via the general modul giving the commands... on the way up, if the glass encounters an obstacle, the force to move glass increases thus drawing more torque from the motor and more juice, and the module shuts off the motor ( retracts it a bit and shuts off). it is the pinch protection. on the way down it operates in similar way, but does not retract glass up. so the wedge will stop the glass travelling at a different stopppig point but will not prevent the disintegration of the clips, as the slightly increase torque applied by the motor will be at a wooden block spot, and that torque will put the force onto the weakened clips. stop operating the windows until you get the replacement clips, and just replace the clips now, before the cable gets all tangled up, and the glass gets scratched, and then you will need to replace all the guts...

sorry for the long explanation...