4/20 is not RNG dependent. Sure sometimes you can have good or bad RNG but its more skill based than luck. The key to winning is to manage your power carefully.
Maybe you dont know but you can stall both freddy and foxy at the same time. When freddy is on her last camera she only enters in the office if the door is open and if you dont have her camera selected. If you leave the door open but you have her camera selected, even when youre not using the camera, she will not enter the office. Now since you can stall foxy on any camera, you can stall both animatronics.
If you need to check on foxy you can close the right door and check on her. You can also use the time when chica is at the door to check too. I hope this helps you.