Rise of the Tomb Raider

This is not a solution, as the solution above covers everything, this is a tip. If you are stuck having the "Gulag Recon" mission not working and it is the last mission you need, where you can't return the items to the guy, which has happened apparently to a lot of people, me included, then uninstall the game (NOT your game save) and disconnect from online. Install the game and play it while offline and return to the guy and the mission will complete. When you reconnect to online this will pop. The problem apparently is the patch that was installed and uninstalling the game does the trick to overcome this glitch.

There are 9 missions needed to get this achievement; 5 in Soviet Installation and 4 in Geothermal Valley.

The one called "Ancient Secrets" requires you to complete 9 optional challenge tombs across the entire map. By the time you get to Geothermal Valley, you will be able to get 8 challenge tombs. You have to progress through the story to the Lost City in order to complete the 9th challenge tomb. You can then fast travel back to the "Ancient Secrets" mission giver and get the achievement.

Soviet Installation:
Communications Breakdown
Dangerous Territory
Gulag Recon
The Unlucky Ones
Misguided Intelligence

Geothermal Valley:
Ancient Secrets
Defensive Strategy
Surveillance Disruption
A Hearty Meal

If you are still having trouble turning in GULAG RECON side quest:

The solution to delete the game, reinstall and play offline without update did not work for me on the XBOX X. Here is what i did to test and solve this issue, which after hours of effort, was finally solved.

1. Attempted to uninstall game, reinstall and play offline. Result: game wouldn’t load, just got Black Screen.
2. Attempted to uninstall the DLCs. RESULT: got error message about a Durango file missing and only option was to Terminate.
3. Reinstalled DLCs. Tried to load game again. Result: BLACK SCREEN. The game simply would not load in offline mode on the XBOX X.

I began to realize this offline solution would not work on the X, so i decided to move my external hard drive to the standard XBOX One console that i still have and try from there.

1. Tried to load game RESULT: Game loaded but only option was to start a new game. Because i was offline, it was also not syncing save file from cloud.
2. Went online to go ahead and download the update, so that i could sync from the cloud after it was done. I was going to go ahead and delete the game again once update was done and game was sync’d, so i could install and turn in that mission offline.
3. I decided to try to load the game mid-update but it was stuck on the resume option. Update was only halfway thru.
4. Tried a few minutes later and it let me load the game AND TURN IN THE MISSION.

I did not need to wait for update to finish, i did not need to uninstall, and reinstall offline without update which was the next plan.

I should get an achievement for all this time and effort required just to turn in one tiny little side mission.

Developers, you need to fix this glitch. You may have solved it on the standard XBOX One, but the solution to uninstall and reinstall/play offline to turn in the one mission, does not work on the XBOX X. At least it didnt for me.

I hope this helps anyone else having same problem, and if so, i hope you still have your standard XBOX ONE.

Hi achievement hunters as most seeking this achievement know there is one mission that you turn in after completion.

I'm sorry but I am working off the assumption that everyone knows which mission it is, anyway the way I found to completing it by rejecting the side mission selecting a new save then completing the objectives in order (top to bottom) and when I went back allowed to turn it in.
The reason I told you to select a new save is because you can't restart the mission but doing it this way allows you to back your save up and retry the mission I hope this helps you.