Britney Spears has been the focus of lip-syncing rumors since the early days of her career. But when her residency at the Planet Hollywood hotel in Las Vegas was announced, her reps made it a point to stress Spears would be singing live during her “Pieces of Me” show.

Attendees of the much-hyped revue of the singer’s biggest hits have praised the theatrics of the massive production. Still, just how much live singing Spears does during her 90-minute set continues to come under scrutiny. And a video posted to Instagram last week may provide the latest proof that Spears is indeed lip-syncing her way through the show.

In the brief clip, Spears experiences a wardrobe malfunction that causes her mic pack to dislodge from the back of her outfit. The falling pack pulled her earpiece away from her mouth. But the singer continued her singing and choreography, with her vocals seeming to remain consistent even with the headpiece briefly away from her mouth.

People have commented on the Instagram video, with the majority saying Spears appears to be obviously lip-syncing in the clip. Fans have also taken to Twitter to express their views on the allegations against the star.

Spears’ “Pieces of Me” features 24 songs and will be running for two years at Planet Hollywood’s AXIS theater. In a review of the show’s opening night for Billboard, writer Keith Caulfield even highlighted that the presence of Spears’s live vocals was sporadic:

The vast majority of the show was lip-synced, and only occasionally were any seemingly live vocals heard. There was a certain thrill in actually hearing Spears breathing into the microphone -- however infrequent.