When Metzenbaum says "I can't begin to thank you, so I won't", Winston's jumpsuit is wrongly colored as Ray's. A moment later the Ghostbusters are shown in the same positions, and this time Winston's suit is the right color.
When Egon, Ray and Winston are in the basement of the opera house, they are wearing tan colored gloves (which they weren't before on the roof). The gloves suddenly disappear when they drop to the floor.
When the Ghostbusters are shown from the back on the scaffolding above the opera stage, there are two Winstons in the same shot and Ray is missing.
When Egon is shooting at the Valkyries on the roof his proton stream first appears in front of Ray, then behind him, then in front of him again. It couldn't have done that without shooting or seriously harming Ray.
When climbing the ladder, the jumpsuit leg above Egon is his jumpsuit but Winston is ahead of him.
When the Ghostbusters are shown hanging from a ladder above the street, the one on the left appears to be wearing a brown jumpsuit like Peter, but Egon is the one in that position.
During the majority of the episode the traps are wrongly colored yellow, and many of the times the warning strips are missing as well.
When Winston says "Maybe the Valkyries are gone" he speaks in Egon's voice.