It appears that if you complete dead city (for the first time) then go back into dead city (to get the kraken and large mutant cards) and enter the dead city streets section from dead city central that you can't then return to dead city central. Basically you are stranded in dead city streets. The doors that lead to dead city central appear inoperable with the exclamation mark in a triangle, with no loading area where you can press "e" to enter dead city central,, and there's no other exit to the area.
I was able to go back and forth through the entire area immediately after completing the first quest that sends you to the Dead City. I found some ingredients that allowed me to make a lock grinder, so I wanted to go back and open the locked doors.
Immediately after completing the level and exiting in the Wasteland near where my vehicle was parked, I turned around and entered through the door I exited from, proceeding through the entire level backwards with no problems.
Numerous mutants respawned and there were mutant bone piles containing loot.