Okay after I played the game again I can say that the endo room isn't the one with the jammed door I think that's the scooping room which isn't unlocked yet I think so to unlock the endo room ,when you first enter the basement with puppet click on third door to your right (not the jammed one) this should allow you to get the endo room unlocked make sure to do this before interacting with mangle or spring traps door because it won't open again and then you can go buy the bat after mangle tells you to kill 4 endos but the extra scrap doesn't work for me so your just gonna have to kill more of them if you want to unlock bigger chest I hope this helps
(Also you should save before endo fights because you might die to rng and you will have to reset from your last save)