Just want to share an experience I had in chapter 10 that might be worth mentioning.
I did my first playthrough on easy without guides and found what I could through exploration. When I reached the large final room of chapter 10, I explored to the central octagonal platform without throwing Trip up to a nearby platform. You can jump down from the octagonal platform to a smaller platform with some orbs, but you have to be in a very precise location to jump down. I tried jumping down with no luck and since I was unable to backtrack to Trip (you can't seem to jump from the first pipe back to the thin beam), I thought I was stuck, so I reloaded checkpoint, which started me back at the point that I entered the large room. Then I finished the chapter and thought nothing of it.
My 2nd playtrough was on Hard and I used this guide to help find the orbs I missed. In chapter 10, I found 5 orbs in plain sight in a hallway leading to the large room mentioned above. I couldn't understand how I missed these orbs in my first playthrough as you would have to make an effort NOT to get them. I was careless in the large room and died fighting the 4 mechs below the octagonal platform, which restarted me at the entrance of the large room. I then finished the chapter. When I exited to main menu, I found I only had 98% of the orbs, which was surprising as I had followed the guide very carefully and felt that I had found them all.
I reloaded the chapter on Easy to try to find the orbs I had missed. As I got back to the hallway before the large room, those 5 orbs in plain sight were there again. I was so confused, but then it made sense- dying/reloading checkpoint in the large room restarts you as if you had just entered the large room, but it doesn't save the orbs collected in the previous hallway. This explains why the 5 orbs weren't counted on either of my first two playthroughs- one had a manual "reload checkpoint" and the other had a death in the large room.