Ecto-1's license plate erroneously reads "ECT-1" during the Conrad's bust.
When Slimer is crouching behind the open door of ECT-1 as chocolate rains down into his mouth, his eyes and nose keep disappearing in various frames.
A wind-up key can be seen on the toy monster's back when it first leaves the factory, but it isn't there in any later shots.
As the toy factory ghost is grabbing discarded toys with it's tentacles, some of these appendages appear to be disconnected from it's body as the full extend of the drawn limbs move into frame.
After Janine informs the Ghostbusters that three ghosts have gone missing from the containment unit, the camera pans across the interior of ECTO-1 to Egon. Winston's shoulder suddenly appears out of nowhere behind Egon, where it should have been visible as soon as Egon slid into frame.