If you're using the 'Altars of Sorrow: Final Phase' as the triumph for tracking it - it tracks it incorrectly. The mini-bosses that spawn also have a tendency count towards that triumph so that number is going to be 3-5x higher than your actual clear count The drop protection is also shared with the ship which you got recently - so your drop protection was reset back to 0 and will start rising again. Drop rate for the ghost starts at 5% and rises by around ~2.3% until its guaranteed after 40. They haven't said whether drop protection rises on just final boss kill or if you need to do all 5 waves for it.