I use a referenced catalogue, so that all my images are on separate hard drive and in folders by year and subject. I have had a few problems lately with folders showing images that when go to look at them in the library they are not there, and I have had to delete the folder and reimport them. Of course doing this means that any adjustments I have made are lost. It happened again today. In 2016 I have a folder Trip to Tamworth which shows as having 31 images, but when I open the folder to view the images there are only 4 that I can see. In explorer or using photoshop Bridge the images are of course there. I cannot re import them and I cannot get them to synchronise, so I have hd to again resort to deleting the folder and re importing. What is happening and how do I resolve the problem?