Right after Lefty crashes the dinner party, Stretch tries to escape. When she is first walking along the passageway, the shadow of the camera crew is visible along the screen left wall moving just ahead of her.
When Leatherface and Chop-Top are leaving the radio station, Stretch walks out the room saying "they can't get away..." If you look to the wall to the right of her as she walks out the room you can see the shadow of the boom moving across.
At the very beginning of the movie the Narrator is telling the story of what happened in the original movie. He states the group was driving a Volkswagon van when they encountered the killers. That is not true; they were driving a Ford Econoline Van.
Lefty walks into the chainsaw shop and lays his sunglasses down on the stump before laying out his money. The glasses are lens down on the stump. Then after Lefty sets down the first saw on the stump he turns to get another saw and the glasses are now upside down with the lenses towards the camera. After he picks up the two smaller saws, the shot changes back to show the stump again and the glasses are back to being lens down like they started.
When Stretch gives Chop-Top the radio station tour she shows him a lamp, but he quickly knocks it out of her hands and it falls onto the floor. But a minute or so later when Leatherface first appears, the lamp is not on the floor and has disappeared.
The goof items below may give away important plot points.
At the radio station, Stretch locks herself in a room to hide from Leatherface. At one point, however, Leatherface breaks into the room and uses his chainsaw to destroy a ceiling fan (which, by the way, was not turned on). But a short time later, if you watch the top of the screen very, very closely, you will see that the ceiling fan appears to not only be restored, but also turned on.
When Lefty and Leatherface fight on the big table, it is covered in food and rubbish. But in shots from under the table showing Drayton talking to himself, you can see through the planks of the table and light is streaming through them, revealing the table is not nearly as dirty as previously seen.
When Leatherface and Lefty fight, Lefty gets up onto the big table; Leatherface attacks him, causing Lefty to fall backwards onto the table. As Lefty falls backwards, he knocks the tall trophy that Drayton won earlier on in the film, off of the table. But in the next shot the trophy stands back up, proudly on the table again.
When Stretch gets the chainsaw from the old woman's corpse in the end, she turns it on and attacks one of the family members with it. Look at the chainsaw. The blades aren't moving, however, you can hear that the chainsaw is 'on', and the family member is still injured by the chainsaw with the unmoving blades.