Other mistake: Episode 1, It's About Time: The clocks in Doc's house have all different times, despite the fact that in the original Back To The Future movie, it was shown that all of Doc's clocks were all the same time, just 25 minutes later than each other.
Other mistake: Episode 1, It's About Time: When Marty puts the fish food in the tank during the experiment, nothing ever comes out of the fish food container despite there being food in the container and hearing the sprinkle.