The mixing of the audio was off-putting. The singers' mics were much higher than the instrumentals. It makes the out-of-breath moments more obvious. Also I think it the backing track off by a hair; just a few milliseconds. Not enough to de-rail the whole performance, but enough to make everything seem uncanny.
Also, the stage here is probably a lot smaller than the one they use for the actual show, so these 5 actors trying to replicate the choreography on a much smaller scale makes things more awkward.