Replacement Parts,Timing belt is tight and yet appears to be slipping several teeth when belt is rotated,

I have a 2005 Subaru Outback 2.5 SOHC. I changed the timing belt, water pump, all the pulleys and had a valve job done. I have done several timing belt changes on different subaru's, and have never had this issue. After the belt is on, both belt and sprocket marks are lined up, i do a full belt revolution and the marks on the belt are no longer lined up with the sprocket marks. Turn the sprockets back to the normal timing marks and they are still lined up, but belt marks are not…….whats going on…John

My car has 180000 miles.
My car has an automatic transmission.