I think there a combination of factors for a short term sell-off before earnings in October and then come February for full year.
1) End of quarter profit taking. Funds will want to book profits for 3rd quarter, going into full year earnings for a lot of companies hat they just don;t know if they will or won;t beat.
2) Governement shutdown plays games with the market and creates unnecessary uncertainty.
3) Stock could be a little ahead of itself going into earnings a month away and market might want to price in those earnings to the downside one last time(58-62/share imo) before the stock continues its glorious climb going into full year results.