Some episodes were skipped during the 1980s syndication of the series which may be where you got the impression that there were missing shows.
The first movie, because it was so violent, led to a lot of Parents groups around the country to demand that local ABC affiliates drop the series because it was perceived as too violent for children's viewing; as more affiliates dropped the show, the ratings also fell;
Brian (who is still mourning the 2004 presidential election and wishing the brother Jeb would leave Florida yesterday
Thank my atheist-self that I didn't grow up in a right-wing, conservative Republican "my-way-or-the-highway and the rest of you are going-to-hell" family.