Flight test today. All is well - and no more "sparkles!" The white single frame dots (sparkles) were just the first signs of the whole image going out.
For those with a similar problem and unsure whether to buy a new camera ribbon cable, it is possible that merely reseating the connectors might do it.
You will still need to remove the camera back plate and the bottom gimbal module cover to reach the 5 connectors. Watch the video to see which ones pull out and which have locking bars. Tools needed are #00 philips and #6 Torx. Needle nose or tweezers are helpful. Takes about an hour - and well worth it!