The director liked Frankie Faison's performance as "Det. Brandt" but in editing didn't feel his voice worked, so it was dubbed by that of African American actor Albert Hall.
By his own admission, director Paul Schrader says that one day he got so stoned on set that he refused to come out of his trailer. A whole day's filming was lost.
When the panther in the hooker's room finally falls asleep after being tranquillized, an overhead view of the room clearly shows a mattress blocking the door. In the next scene when Yates enters the room, there is nothing impeding him from opening the door.
During the scene where the panther is in the hooker's room and Oliver is cleaning the window on the outside of the building, there is no silhouette on the inside shot of the room visible.