Alright, I took this metal hinge out by undoing the screws. Springs popped out as I expected, but I managed to turn it a bit and slide this plastic piece back in. Then I tucked springs back next to the bolts. So apparently when I tightened both bolts too much they pressed against this plastic part too much and prevented a hinge from moving when folding. This applied too much pressure on a plastic part and it popped off. Loosening the bolts properly and balancing them out so they are both tight but loose enought to allow hinge movement resulted in a plastic piece staying in place and folding mechanism working as it should. I'm happy I didn't break anything, hopefully nothing cracks when I commute 20 miles tomorrow haha.