Has anyone actually genuinely beat this mode? Honest question. Sandy is ruining every run I have.

I beat the game 100% and I will tell you this, for me Sandy was very predictable unlike Suki and Crystal,  I never used the cameras, aside from the music box, the reason is, because they are so fast, milkmean can ruin your run when you shut the door to early and the last character (I can't remember their name at the top of my head) isn't really a threat to me and I'm not gonna lie it's quite the challenge because sometimes they attack you at the same time

It’s possible.

It just takes a lot of trial and error as well as learning the characters and their attack patterns from the previous nights and mastering the timing of when to do what while also trying your best to conserve as much power as possible.