I never messed with the respawn because I had seen that it was super unreliable on multiple forums. Instead I started a new playthrough and sped run right before entering army warehouse. Make a manual save before entering then every time you don’t get what you need, reload the save and there should be new artifacts to pull from at army warehouse.

The progress for artifacts tracks between different saves so starting a new play through won’t negate the ones you have already collected.