Strange video shadow noise glitch on a7sii?

[b_funk]

I've been shooting a doc on the a7sii. WB is always set to manual, either incandescent or a kelvin setting. However, at times I'm noticing a strange "strobing" color shift in the footage and it's driving me crazy.

You can view a 4k sample here: https://bit.ly/2tO5dQh

The first clip in the above video is at 1600, the record player shot may be 3200. Picture Profile 7. High ISO NR was off I believe, but that should not kick in at 1600, right? It's mostly in the shadows and will switch back and forth a frame at a time ... but only sometimes.

Anyone experienced this before?

 

Edited June 29, 2018 by b_funk
title more accurate