Missing a part in Monkey Caves Zone 1

[PaleVoyager]

I've scoured this zone, and even followed the video guide to the letter, but for some reason, one of the parts aren't appearing.

I know for sure I have the part you get by breaking the rock that becomes a bridge, but as for the others, not certain. Are there any objectives I'm not understanding? Like killing every enemy?


(EDIT: Wow, apparently that's exactly what I had to do. My apologies.)