Sentinel Reward Tiles Bugged - Early Campaign

In the early campaign it is possible to get a unique reward tile on a monster but have no unique drop. Testing took a while and was limited but I ran between mud flats and submerged on a lvl 24 scion until I got sentinels with the unique reward tile and it hit a mob (takes a while as its normally 1.0-1.4% chance that I saw!).

2/2 of those unique tile rewards I generated did not drop a unique item.