So yeah when you get the first cave key that is very close to the vent 1 if you dont go the vent with it and you go further it may somehow glitch out and it won't work latter as i found out. It wanted me to find the key even though i found it missed the vent 1 did vent 2 and 3 went back and couldn't do vent 1 because of the glitch.
Meaning after you find the key and then go to the not so far satchel just look over where you can jump to another area where the satchel was that is the place where vent 1 is.

Not 100% sure if it really glitched or i missed a cave key
edit:
Actually missed a cave key on a wodden platform after the last teleporter, had to jump down a certain area close to the secret with the burrower or what that weapon is called, there are 4 blue healts close.