When Linda is driving the truck, the humanoid breaks some of the windshield on the driver's side. But after he falls off the hood, nearly all of the windshield on the driver's side is gone.
After Johnny Eagle takes the couple back to his cabin to help clean the fish for dinner, it's already dark. When Slattery and crew are coming upriver to his cabin, it's still dusk.
When the creatures are attacking the townspeople while celebrating at the Salmon Festival (about 1h 05m into the film), you can hear the screams are being played on a loop at approximately 10 second intervals.
The first attack scene on the boat when the winch engine is heard running then runs out of fuel during the conversation with the boy there is no spark plug wire going to the engine's spark plug, so being out of fuel is the least of the problems.
Once the humanoids break through the bottom of the dock, the commotion starts. And the first eight or nine seconds of screaming is "looped" and continually heard throughout the rest of the attack at the carnival.
In the first boat sequence, the winch is supposedly under a lot of strain but all of the lines are loose. They would be tight if the winch motor was working to attempt to pull in the net.
When Jackie is pulled underwater by a humanoid, you can see that the film was merely run in reverse, (hence the water rolling UP his head) from the first time he emerged after falling in.