Goofs

In some shots of the bus, the front wheel is in front of the door. In other shots, it's behind the door.

Snoopy blows up his raft and it's clearly a rubber ring with no base. Later he drops things into it and it shows a base, then it's in the water and water is splashing through the middle of it.

After Peppermint Patty forces the boys to sleep outside the cabin that the boys found, the ground is covered with snow when they wake up the next morning. Snow is very rare in the summer, even in the Rockies.

Incorrectly Regarded as a Goof: The girls were listening to a radio broadcast where the announcer alerted travelers in the "high country" to "put on chains immediately". Lucy then found herself explaining to Sally that he was talking about mountain climbers chaining to one another. The radio announcer was actually referring to people putting tire chains on their vehicles to be able to drive through the ice and snow.

When the boys are leaving the cabin, Schroeder disappears for a frame or two as he's passing Lucy.

Although the three groups were competing with each other during the raft race, notice how there were no other groups around that were even in the race.

When Brutus is chasing Woodstock, they run past the bullies, who were still trying to get their raft off the rocks. After running through them, they all end up as they were after fighting with one another earlier on, including Bully #2 coming to first.

When Charlie Brown and Sally are being bullied by the "We're number one" guys, Snoopy comes along and says "Wait until my brother's dog gets here. Boy, he'll show you. He'll take care of your dog!" However, the bullies' pet is actually a bobcat.