For some reason this often happens when leaving X-18 after the first visit. I assume that there is a corrupted NPC (stalker_bandit_5?) that the game is trying to spawn outside. Before exiting X-18, try using the ESC+F2 teleport menu to dvalley. This should bypass the local area and put you in the bandit base - but be careful, it is probably full of soldiers by now. You should now be able to return to the X-18 compound if you still need to, or just give it a wide berth.
I also suggest that you PM aleks1970 (click on the banner picture above and then on any aleks1970 link) as he may want to investigate.