When the boys and Donna are toasting Eric, Eric's can is upside down, yet the can opening is up.
The bathroom at The Hub is on the opposite side of the building as opposed to other episodes.
In the opening scene of the premiere episode, the boys are looking at a Playboy centerfold, circa 1976. However, the magazine is perfect bound, not saddle stitched (stapled) as Playboys were at that time.
When Coca Cola bottles are seen in this episode, they all have a red label stuck to them. However, Coca Cola didn't have printed labels in 1976, they had full-glass bottles with the Coca Cola logo molded in the glass. In later episodes, the correct bottles are used.
In 1976, a cassette deck in any form would have been exotic and very expensive. Eight-track was the standard, and cassette players in cars weren't really a thing until the late 70s early-80s.
Eric's shirt pattern in the party scene is definitely not 1970s.
When Jackie and Kelso are talking about the concert. Jackie says "Todd Lunderman" instead of "Todd Rundgren". The closed captions/subtitles will show that she says "Todd Rundgren" but she said "Todd Lunderman".
In the scene where Red and Kitty are lecturing Eric about the responsibilities of a car, the shadow of the camera can be seen on the right side of the screen.