The Metal Detector’s viewmodel is being rendered in the same scene as the world. As such, it is clipping with nearby geometry.
Have Metal Detector on the hotbar. Select Metal Detector from the hotbar and stand close to a wall.
The normal behavior.
The issue the bug caused.
Other first person games will have a viewmodel rendered in a separate frame and will overlay it on to the main scene. A Sneaky Trick Most FPS Games Use - YouTube