Just got my OSSC today with firmware 0.76, hooked up my NES (with NESRGB) and got this:
It flickers between straight vertical and that distorted bend.
Disabling “Allow TVP HPLL2x” makes a very slight improvement, if any. Adjusting analog sync LPF makes no noticeable improvement, and just shifts the image horizontally.
EDIT: I downgraded to 0.75 and still have the same problem.