After returning to the map, a Panzer will spawn. Make sure you do not end the round, before you input the code.
Head to the tesla trap, you can place the fuses you picked up.
Then, go to the right side, and there should be a meter with an arrow pointing to the word destroy. Interact with it so that it is pointing to protect.
At this point if you are in Co-Op, Hellhounds will begin to spawn infinitely, so be weary of them.
Now approach a set of green monitors next to the clock tower and Wunderfizz, and four symbols should appear on the monitors.
@anonymous @RadZakpak @NaBrZHunterpictures need to be added
You must input the three symbol sequence that Groph entered by interacting with the monitors. If done correctly, you can return to the teleporter room, and the safe will now be open, with some items inside to pick up.
If you input the wrong code or advance the round so the code is different, you must hunt down the wisps again on the next round and watch Groph input a new code.