Hi Gstaff!
I found it had occurred during the "Lost Patrol" mission for the brotherhood of steel.
In another post some people attribute it to the National guard Training Yard location. I however had it occur once i had approached the first beacon site although i was looking around the Med Tec Facility north of the objective location.
I traveled further north to the Asylum and killed the guards out the front and this is when i first tried to fast travel back to the Med facility and it just wouldn't let me there was no notice at this point.
I saved and reloaded now it was showing the "fast travel is currently unavailable from this location" it shows the message when trying to fast travel and when just swapping back a forward from the map on the Pipboy.
completed quests:
Out of time
When freedom calls
Jewel of the commonwealth
The first step
Sanctuary
Raider troubles at Oberland station
Fire support
Call to arms
Semper invicta
Unlikely valentine
Getting a clue
Reunions
Shadow of steel
(various "Cleansing the commonwealth" and "Quartermastery")
Tour of duty
Show no mercy
(various "Cleansing the commonwealth" and "Quartermastery")
The gilded grasshopper
Feeding the troops
Learning curve X 2
(various "Cleansing the commonwealth" and "Quartermastery")
Last voyage of the USS Constitution
The lost Patrol
The Lost Patrol is completed as i walked all the way to the Prydwen to turn it in hoping that the quest ending would clear it. It did not work. I was undertaking the mission in Brotherhood power armor and with Paladin Danse as a companion.
At 42 hours and level 26 i may just abandon this character. Please let us know if there is a fix we can do for this or if we have to wait for a patch that would be very much appreciated.