It literally sounds like guitar wow pedel when it happens. It's due to the fluctuation of the speed of the turntable. In that video the turntable seems like Au

It literally sounds like guitar wow pedel when it happens. It's due to the fluctuation of the speed of the turntable. In that video the turntable seems like Audio Technica's Technics 1200sl knock-off version which is quite infamous for instability, it seems fine in short video though. Very impressive nonetheless.