Cycles Procedure Background Appears, then fades with each render iteration

Greetings all. I’ve been struggling to create a procedural world background, pretty simple, using the voronoi texture. My goal is creating a simple star field for planets and moons.

Up until this morning, I was having no luck. I’ve been follow several different tutorials on the subject. To simplify, I’ve removed pretty much everything from the project except the background (world) and camera.

I noticed that I did see a starfield in the first iteration of the render, but by the 3rd iteration, it completely disappears. To test, I reduced render samples to 1 and low and behold the starfield was in the render. Of course, the rest of my objects were of very low quality, so this change isn’t going to work.

I’m stuck and hoping for some insight as to where to look to fix.

Please help. Thanks.