So, I decided to go back to Bloodborne after all this time, and I found a Red Jelly in the Great Pthumeru Dungeon, second floor, main area.
The chest spawns in a wall, but I guess the devs never noticed, and didn't remove it. This is NOT in a root chalice, so this isn't the result of faulty object placement in a random map. This will be here every time to make this chalice.
Since spotting a chest in the wall will be difficult, I'll give more precise directions.
Great Pthumeru Chalice Dungeon
Pass the Primary Area and go straight to the Main area [second lamp].
Proceed to the round room with a spiral stair case, and climb said stairs [beware of trap].
Go through the only exit at the top of the stairs, and proceed down the hall into the next room.
This should be on the upper most level of a large room. Remain on the upper level and go to the complete opposite side of the room.
Go through another hall into another round room, but this one is an elevator room.
Remain on the upper level yet again, and hug the left wall. You should get a prompt to open a chest after making a quarter turn around the room.
1 Red Jelly