Zedd Waves - S2-E26
Other mistake: After the shot changes from Zedd yelling at Goldar to Tommy, Kim, and Billy in the park, for a brief second, you can see the three actors were standing and waiting for the cue to begin walking; most noticeably with Tommy who puts a little jump into his first step from standing.
Answer: Probably to save on costs of filming the same scene. In the reused shots they have always morphed so you can't see the actors. They just have to pay them to do voice-overs rather than the entire scene.
Ssiscool ★