Anyone else with a D800 + 17-35 AFS 2.8 getting really mushy corners ?

Thanks - yeah maybe I will have it serviced - then be sure to stop it way down. I hate to part with it as it fits my needs well - good info on the 16-25 f4 -  I was never very excited by the 16-35 f4 for whatever reason so I never even considered it.