The police helicopters' registrations start with "LZ" which means they are registered in Bulgaria, not the US which have an "N". Meaning it has not been filmed in the Washington State forests but in Bulgaria.
When Ray is showing Sandra how to use the pistol, he says that "this gun has no safety... just pull the trigger." This model revolver does have a slide safety located just in front of the grip on the left side.
Everyone's (especially the bad guys) clothes stay clean and neat even after spending the night in the wet forest without shelter, helicopter crash, etc. Frank's suit seems to stay pressed no matter what.
At around 38 minutes into the movie, when Johnson gives their coordinates via radio to Davis, he says "40.083 North, 25.55 West". That's in the middle of the Atlantic ocean, between Europe and North America. Washington state, where the movie is supposed to take place, lies approximately between Western longitudes 117 and 124 and Northern latitudes 46 and 49.
At the barbecue, a DJ announces the radio station's call-sign as "WKGV." This is geographically incorrect. In Washington State, and most of the U.S. states west of the Mississippi River, radio station call-signs begin with the letter K.
After the close up of Lockland and Sandra losing their balance on the bridge they go to a wide shot showing Carden following them. He then is seen helping Sandra up. At that point one hand crosses the other and he appears to have no handcuffs on. Realizing his mistake the actor quickly returns his hands to handcuffed position.
It is reported to the FBI onsite that there were just three sets of foot prints leading from the river, when actually there would have been more due to the bad guys converging on the area where Ray pulled Frank and the Marshall out of the water.
When the shootings occur in the woods at the funeral, a silenced rifle is used. However, the shootings occur close enough to the funeral that you can clearly hear the service, so the funeral attendees should be able to clearly hear even a silenced gunshot (silencers don't work like the movies depict, the shot is still identifiable as a shot, just not as loud: it's not a soft pop, especially not with a rifle).
The goof items below may give away important plot points.
The FBI say they picked up the trail of Chris, Ray and Frank by the river where they found the U.S. Marshal. This is unlikely since the body of the dead U.S. Marshal was sent down stream by the guys chasing Chris, Ray and Frank.
When the younger Hammond is killed by being pushed in front of the speeding SUV, a careful look reveals him "falling" in front of Cordell, not directly in front of the SUV, so that the SUV would actually miss his body.