The suit in Night 4 has the individually moving faceplates just like the Funtime animatronics, so It's most likely the suit of an unused Funtime Animatronic (most likely Funtime Chica judging by the location of the plates)
Well there's only 2 springlock suits iirc. They describe Spring Bonnie's springlocks as being "dangerous to the point where breathing on them was dangerous", right? And Baby did say "your breathing is making them come loose".
Ok spring trap exists not IN sister location but at the Time of sister location the funtimes were made at the time of forebears and FNaF 3 takes place in 2017 and pizzeria simulator sometime in 2018 meaning that William was also killed the same year as Micheal was bit 1987 2017 - 30 equals 1987 spring trap has been in the backroom for 30 years this is completely off topic I was just thinking and thought it was noteworthy