I use FSLTL for traffic and have switched off the default live traffic. The problem seems to have been solved, did a quick return flight from EGBB to EGNX to EGBB and the traffic was parked at the gates as expected upon return to EGBB. However, just before departing back to EGBB I did encounter this bug as well, Can’t Hear ATC and Other Aircraft after SU11 and lost all voices from ATC except the my own pilot.