the game uses a noise to tell you how far away they are, it's a radar ping. the first enemy is visible but every one after that is invisible and they tend to spawn about half a screen away from you, and only when you enter the room. if you're describing them just appearing out of nowhere, make sure to listen for the length of time between the pings to know how far they are from you. if you are doing that, then yeah it was a bug lol. thank you for checking it out and leaving feedback though! i should probably put a 'headphones recommended' thing on there and gate the radar so the player has to pick it up to progress.