Hi, I would appreciate any feedback for owners of the 80v Greenworks mower from Costco. First use I immediately noticed a shrill sound from the motor, almost like a one pitch siren. It's not super loud, but quite annoying. Is this normal for this mower? I also have a 60v Greenworks mower (which I love) purchased in 2019, and it does not have that sound. Any thoughts? Thanks!