Derelict Mansion Map bug

This happened to me more than once in last few days, whereas I clear Derelict Mansion, kill the map boss and it dropps no loot whatsoever, two times in a row to be precise. This is not a lootfilter issue either, thank you. My best guess would be that I kill both bosses in a relatively small time window from one another, which somehow interacts with some loot drop trigger or something