For those who are having trouble with 4/20 mode, here is a guide to help you out from someone who beat it within the first hour of attempts.
First, wear headphones. You cannot be using the light constantly to be checking the doors, and since bonnie and chika will always make a walking sound when they are at your door, it's vital to be able to hear that.
I have a lot of tips about how to manage the animatronics, but honestly it doesn't matter. 4/20 mode is EASY, so it doesn't matter how you deal with bonnie and chika so long as you can consistently stop their attacks while not being excessive. If you really are struggling, when you see them at your door close it and wait 5 seconds. They should leave by then, though you can use the lights to confirm. Freddy isn't even a threat until 4 am, and all you have to do is keep the cam on her final position OR close the left door when looking in the cams.
The real killer is foxy. Or rather, how bad you are at managing power with foxy. Either you're flipping cams waaaaaaay to much, losing tons of power in the process, or not flipping cams at all and getting 4+ attacks from foxy.
Keep cams on foxy until freddy becomes a threat. With foxy, check her very infrequently throughout the night. You are only checking to see if she's moved or not. This means for the whole night you are spending time idle, which is good because you lose the least amount of power this way. Only until right when she is about to attack, aka when she is out of the curtain and crawling on the floor, do you stall her.
When stalling foxy, check cams every 2 seconds for 3 seconds before closing and repeating. The reason you keep cams on her for so long is because this will actually stall her. Even if you suck at every part of 4/20 mode, just try holding cams on foxy for longer and you'll notice that she doesn't attack as often. She still will, but if you can keep it down to 3 attacks in a night you should have enough power to win.
I can give more tips, but try the foxy tip first and see if that makes it easier.