I found the problem. During the download or after disconnecting the images were being corrupted by a DW external hard drive that is on a lead and USB. Disconnected the external hard drive and t shot about 70 scrap images and a movie and all images and movie came out fine. I tried it with a card reader when I was having problems and it didn't make any difference. I prefer to use a permanently plumbed in USB cable rather than disturb the card and chance damaging the camera card door. The images come off the camera as RAW and I convert to Jpegs if required always dumping the images not required. The images used to be fine on the camera. Thanks for your interest and advice.