Patzer

The first sight of Zimmermann in the film was him walking in the street with his son at the beginning with a scar above his left eye. He bumps his head later in the movie and is covered by a plaster which he rips off in the 2nd half of the film...

For the second hit, Zimmerman is given a revolver with a suppressor (aka silencer) - which does not work on that type of pistol. This is a common mistake in movies.

The shadow of the helicopter filming is visible during the aerial shot of the train at about 1:27.

About 1 hour & 8 minutes into the film the sound boom wanders into the shot. It's the scene where the character Minot is paying off Zimmerman under the bridge/pier.