A FlyValan ATR 72-500 had originally taken off from Bucharest Otopeni and was scheduled to fly to Oradea. The crew had to stop the climb out of Bucharest Otopeni at 7000ft due to a problem with the cabin pressure. They returned to Bucharest for a safe landing around 20 minutes after departure.
Passengers reported they were asked to disembark. Maintenance took care of the aircraft, they were subsequently told the problem was fixed and they boarded again. The captain, however, indicated the aircraft wasn’t fit to fly, they were asked to disembark again, maintenance again worked on the aircraft.
They embarked a third time, and departed Bucharest again and was climbing through FL090 when the crew stopped the climb due to the same problem again. They returned once again to Otopeni Airport for another landing about 25 minutes after the second departure and about 5 hours after the first departure.
Luckily the airline had a replacement Boeing 737-500 reach Oradea with a delay of 6.5 hours.