As Byron gets up to leave Ashley's trailer, you can see the tip of the beer bottle he's holding. In the next shot it's gone.
The story takes place in August but azaleas and dogwoods are blooming on the grounds of Graceland, revealing the actual time of filming to be in April.
The closing scenes are supposedly set during the candlelight vigil that takes place each year at Graceland on the anniversary of Elvis Presley's death in August, which is a very hot month in Memphis, TN. However, in the closeup shots of Schaech and Fonda, the actors' breath is clearly visible. This is because the shoot actually took place in early spring, during unusually cold weather for Memphis.
Marilyn's lips don't match the singing in her song.