Bug: Can't open locked northern checkpoint door

[Ole "Slim Jolo" the Hobo Hero]

In the early game as you leave Lesser Zone after siding with stalkers in the early missions, you're supposed to take a key to get out of the northern checkpoint.

At the checkpoint, there's a little checkpoint gaurd house with a ground floor door you're supposed to unlocked and no means of accessing the second floor, which has a grav anomaly hanging over it, and no way to access other side of the bridge / checkpoint from there.

Key seems like it vanished from inventory, maybe after emission, sleeping etc, and while quest marker says to go to northern checkpoint, it actually points at gaffer but with 0 options to interact, just like the locked door has 0 options to interact.

Softlocked?

[SLIK]

I'm having the same issue. I had the key, and now it's vanished. I hardly ever take roads, so ♥♥♥♥ knows where it went