So we start with the fact that the original bleeder had a fault causing air to be blasted into the braking system. Reporting to Vevor the fault and exchanging photos etc concluded that the bladder had failed. Rather than exchange instantly I was asked to take spare parts and replace the part myself. Fine if it was expedient on time. Anyway excellent support had the part to me quickly and I replaced the faulty part taking care as the original just had been badly assembled and had burst. Lost 10GBP value of wasted brake fluid so not so happy. When all repaired unit works really well.