Deliberate mistake: During the scene with the malfunctioning juice maker, when it goes nuts there is no possible way that all that juice and pulp could have come from just one orange. (00:22:45)
Deliberate mistake: When the Gremlins take the tractor, from inside, the plastic around the cab is clear for visibility, but seen from outside, it's all black or opaque to hide the stunt driver.
Deliberate mistake: When in the bar, or playing with the chainsaw, all objects swap from their real size to really tiny and perfect for Gremlins to grab.
Deliberate mistake: At the bar many of the gremlins are drinking beer and getting wet from it but nothing happens.
Answer: The original film was released before the PG-13 rating existed (it was one of the films responsible for its creation). Producers decided to remove some of the language and violence for the DVD release to avoid complaints about the PG rating.