This is caused by the new resampling filters. There's some overshoot in the interpolation. When you turn it off, this goes away. (they're on by default)
It looks like there's some sort of sinc function at the discontinuity on the phasor. It's pretty cool to watch. Also, check out the spectroscope for interpolation on or off. You can really see the resampling filters blocking everything above the new Nyquist rate.
If you look at the scope~ on the left you'll see a smoothed noise function. Not a bug, just not maybe what you expected.