I didn’t want to put this in bugs just yet as I know that this can be “seen” in real life, but … I’m parked up at EGHF (Lee-on-Solent) in my Daher Kodiak 100, and I have just watched another player take off in what I believe a Bell helicopter. Even though I could hear his rotors turning and saw him rise in the air (very well done if I may say), his rotor blades appeared not to be turning. Not sure if this is a bug or that weird thing you sometimes see in real life when filming a helicopter, and the blades appear not to turn (something to do with the camera shutter speed matching that of the rotors I believe).
Here is a band aid:
There is a logged bug topic here for the Bell 407: