I have had many problems with boolean operations also. One of the tell-tale sign a boolean will fail is if an object enters a surface and exits a surface which borders a hole. I will usually try slight positioning adjustments (5 times before I give up). I also will change surface normals and surface positions. Usually after too much trying it succeeds and I get a carpel tunnel flare up. The rendering fails seem to be the result of a geometric anomally that the computer generates when calculating the surface intersection. Not much help but you are not alone.