Optional mission not starting in soviet installation?

Hi,

I'm backtracking to finish some stuff and there us an optional mission in a cave that should start, but nothing is happening. There is no one there or no prompts. I believe it may be called Gulag Recon after looking at a guide. Any one else have issues?

Please help.

I didn't find the right solution from the Internet.

References:
www.xboxachbhgvievements.com/forum/showthread.php?t=632587
Startup Explainer


Thanks!