Good question. Compared to my naturalization experience, and that of others who underwent the process at the same time as I, USCIS really seems to have gotten their act together. I'd be curious to know the reason behind the recent check cashing/receipting delays.
I think it has to do with statistics. As long as they deal with a certain number of applications at a time, they will keep within the "acceptable" processing time which they finally manage to accomplish. In order words whatever application they don't touch is not part of the statistics. (Just an opinion from the economist in me...)