Not as good as first prints (leaning towards one star)

I'm not sure why, but some of the prints would randomly be blurry if that makes sense. As if the printer heads were mal-aligned. Anyway, it didn't happen on the majority of them otherwise I would be more upset. I thought the whole point of sending in a 300 dpi image was so that this wouldn't happen. My prints don't look anywhere as clear as the proof sheet they sent me. I hope this doesn't happen again.