Here is a full guide of all the bunker key location.
This is going to be a guide for all the bunker key location because some of them are out of the way others aren’t this is just here to help you find them faster. This might be out of order for you but don’t worry all the levels with bunkers will be in this guide
When your by the fall checkpoint you want to go left and slide under the chain once under the chain you should find a spaceship and a box next to it. hit interact and the bunker will unlock
The forged pass
Once you have gone pass the first ladder after the jump pad you want to look at the right you should see a cave and alot of wall runs to a space ship there you will find a box with a bunker key in it
In the area before the arena in the water there will be a space ship with a box with the bunker key inside
Right after the first zipline ride if you look back you should find the space ship with a box and a bunker key inside
Thats all the bunkers key location and the levels i didn’t say don’t have a bunker like twin jungle, sentinel, and stone isle