Goofs

Nicole Kidman's hair color changes from reddish to blond several times.

In the second bath scene near the end, the amount of mud on Sean's face changes between shots.

The first scene is following from behind, a man in black hoodie, running on a snow covered road, surrounding a park. His left shoe/boot is obviously untied. Since he died of a heart attack, an untied shoe was not intended.

People's shoes often become untied (or are left untied intentionally). In no way can this be considered a Goof, especially as the "intent" of the writers and director cannot be divined.