Williams classic quote " I always Come back" is most likely a reference to the Five Nights at Freddy's 3 trailer " He will come back, He ALWAYS does".Scraptrap speaks in a southeastern British accent.Instead of making moaning/indescribable sounds, He speaks.This proves that against all odds he's still alive and not just possessing the suit. During his salvage minigame, if Scraptrap is very close to jumpscaring you, you will hear his heart beat.
After the fire at Fazbear's Fright somewhere between the events of Sister location Springtrap found a way to get new parts to rebuild himself.