Other mistake: The fire at the used cars dealership recycles several shots from the petrol station fire in Series 6 episode 7. These include shots of burning petrol on the ground and a Renault car with the registration mark B649 CLY exploding.
Other mistake: When the opening credits are shown, the door to the basement is in the kitchen. In the beginning of the series the door is still in the kitchen, but in later seasons the basement door is in the laundry room, but in the opening credits it is still in the kitchen.
Suggested correction: I had noticed the same thing and thought it was a continuity mistake. However, in Season 3, Dan mentioned building the back service porch where Roseanne does the laundry. There are two basement accesses, the one in the kitchen, and what was probably the outside entrance in the backyard that is now enclosed inside the service porch. The family prefers using that one. Most houses, mine own included, have multiple basement access, one inside the house and one outside. In my state, it's a building code requirement.
Other mistake: During the 3-nightmare sequences, there are 25 students, with all desks full. However, 1 desk should have been left open as Kevin appears in the dreams, meaning there should only be 24 students.