When the false Voltron surfaces its Right Leg segues to, and in the last shot of actual Voltron its Right Leg is, yellow, the color of the Left Leg, instead of blue.
As Voltron flies from Arus, the muzzles of Red and Green Lion are colored in, instead of silver-white.
Lotor's lip-movements are too many for the syllables he speaks when giving an order to stun (this would have been a dub from a Japanese order to shoot to kill).
When a missile aims for the Right Arm of Voltron, Keith says "Not this one, Hunk" as a signal to avoid it, and when the Red and Green Lions separate from the main body of Voltron and attack the fake one with Blazing Sword, he says (referring to Red Lion) "OK, Hunk, disarm 'im." Lance pilots the Red Lion. Hunk pilots the Yellow Lion.