AD725: is it dot crawl - and what to do about it?
The artifacts you're seeing are due to limitations in your luma trap Y/C separation technique.   So you are seeing interleaved chroma/luma aliasing at a low harmonic difference frequency.  Increasing the Q may reduce this but possibly also increase group delay with ghosting.

You might try to reduce the contrast (Gain) in the Y or saturation gain in the  C channel of signal being created.

The AD745 chip uses a prefilter and a 8Fsc sampling clock after the delay line followed by an LC LPF filter for Chroma.

Apparently the CXA1145 is even better than the CXA1645 for these annoying  “jail bars” when the clocks are sync’d.

If you use S-Video the luma and chroma are always kept separate and do not have this problem.  

Ps. A tripod or resting spot, helps with the GIF motion. ;)