I have tried tons of settings and console commands, but nothing seems to fix it so far (nothing to do with TSR).
Anyone?
(Edit: tested both 5.5 and 5.6)
With Nanite:
Without Nanite:
I strongly suspect this has something to do with the way nanite calculates which mipmap to use. Traditional rendering uses ddx/ddy - otherwise known as screen space derivatives.
Nanite uses a different form of analytics to decide which mip is shown. This is probably resulting in the nanite option showing more texture detail at a distance, causing the moire pattern.
The simplest solution is probably to just slightly bias mips as needed.