A "terminal setback" is pretty similar to extinction, by definition. There are a few examples: life forming a single navel-gazing wireheading organism would be a pretty "terminal" setback.

However, we face many more roadblocks on the way to forming a galactic civilization. We have to master, intelligence, nanotechnology, fusion, space flight, and then we have to agree to devote large quantities of resources to interstellar colonisation.

I fully expect that we will do those things - but I take such a more detailed analysis as evidence that we are past most of the roadblocks - not as evidence that we are likely to accidentally annihilate ourselves!