shabbat elevator

Question

I have a shabbat elevator that stops at each floor automatically, it waits 5 seconds and then goes to the next floor. when it is at your floor you can open the door and get in and then it continues its cycle. if you hold the door open too long it will delay the elevator going to the next floor. once you close the door it will wait the 5 seconds and then go to the next floor. Is this ok? can I purposely hold the door open to stop it from going up and down and then close it when I want it to work again. (It seems it would all fall under grama.)