There is a Guardian’s Lair that looks like a sewer and has 7 columns. The Pit boss affixes/shadows can spawn beneath the base of the columns, the base obfuscating the floor graphic indicating a shadow will spawn there. This makes it so the shadow spawns without any indication of it being there resulting in player death.
Platform: Xbox One X
Reproduce: Fight Pit Guardian in this Guardian’s Lair and stand hugging any of the columns where the base obfuscates the player’s feet and wait for shadow affix to spawn near you. It sometimes happens that the floor indication of the shadow is completely or almost completely covered by the column’s base. It’s most notable on the northern part of the north-most column.