Ryo Shoots an Own Goal - S1-E23
Other mistake: After the own goal, Misugi and Yayoi are talking. Behind Misugi, someone is holding a small book open without using their hands. (00:15:30)
Other mistake: When Teela is at Snake Mountain, she overhears TrapJaw saying how Skeletor's electrical creature will control all of the machines at the palace. When Teela returns to He-Man, she says that the creature Skeletor created is called Byte. There's no way for Teela to know the name of the creature, since TrapJaw never referred to it by name. (00:14:24 - 00:15:20)