I hope someone can help. I am stuck at the Base Camp and unable to use fast travel with no other means of exit.

I made it to the point of no return in the lost city, and decided to use fast travel from the Final Precipice camp to the Supply Store to purchase the rifle Grenade Launcher for the final part of the game.

After this was purchased I went back to the adjacent camp site to fast travel back but option was unavailable. I tried subsequent camp sites within the Soviet Installation but all fast travel was unavailable. I hoped loading a new area would resolve this, so I made way into the research base, as this was the story progression, and zip lined all the way to the base camp. Unfortunately the camp site there also does not offer fast travel and now there is no other means of exit so I am now stuck there and have nowhere to travel.

Unfortunately I have no save slots so I cannot revert to an earlier part of the game. How do I get out of this area in order to finish the game? The only other noticeable factor is that it is night time and with low visibility.

This the 20 Year Celebration version on PS4