Actually that's the whole reason Beta readers (and Editors) are needed, you can't find your mistakes easily when you know what the "true" version should be.
That's also the reason I recommend writers to never critique their own stories unless a lot of time passes, because the words they choose will make sense all the time when they have the actual scenes in their heads.
Well, though I know this... I'm guilty of publishing fast, cause I don't really care... But anything that is published for the readers sake (not myself) needs to be proof read, preferably by someone else before publishing.
When I'm publishing fast on this blog, I tend to do the proofreading as I go. I know some folks out there like to write up an entire rough draft, then clean after. For me, the beginning has been completed by the time I get to the end.