Can you try a rainbow colorwash or chase or something that would cause the color value to change every tick? Even a fast shimmer between two very close values. By default with xLights, if nothing changes in a universe, it will only send it out every 500ms instead of every 50ms. I'm wondering if the CCR's cannot handle that and require it more often.
If you have a Mac, I'd be happy to give you a custom build of xlights that sends out more often if you want to try it. :-)
Dan