Lots of people still consider songs like Peacock, Hummingbird Heartbeat and Dressin' Up to be perfect single choices, but if you think about it, all of them have one thing in common; sex. I'm not saying her other singles weren't sexualised, because a lot of them were, just not to the extent that these three are. For that reason, they may not have faired as well as some of her other singles due to her image at the time.
Overall, I don't think that there was one misstep during the entire era. It was pretty much perfect. Who else wouldn't want 8 Top 3 singles, including 6 #1's and a record-tying 5 from one album?