Moving the motor to certain initial position I was assisting my child in EV3 missions, specifically, the 3rd mission of TRACK3R, the one where the robot has to grab two tires and put them elsewhere.

The mission requires to manipulate the Medium motor at about 90 degree turns: 90 degrees anti-clockwise means "close" and 90 degrees clockwise means "open".

It quickly becomes a hassle to reset the hand to the initial position, from whatever position is was left after the program exited. Forcing the motor to turn until it can't no more is not a solution, because the motor gets stuck, green LEDs on the brick are blinking, and the action block in the software does not advance.
If you are using the mode "turn by N degrees", it will become stuck. However, you can try using the other mode - "turn for N seconds" and it will work. It will work because the first mode will keep trying to run the motor until the motor turns exactly by 90 degrees, and so the program will appear stuck. In the second mode the motor will be on for specified number of seconds and then the program will go to the next block even if the rotation was less than 90 degrees.