A similar event has been discussed elsewhere and whilst there is no question that one or more pilots seriously oversped the aircraft, which was not surprisingly a serious disciplinary offence, the expert view is that it was not possible to actually break the sound barrier. At least one pilot claimed (much later for the above reason) that he went supersonic and he may well genuinely have thought he did. But there was no way of proving it and the aerodynamic and instrumentation problems point against this.