I've been dealing with the same issue you described. I discovered something rather awkward too. As you said, it only happens with the phone is in portrait mode...I've noticed that too. The last time I did a wipe, I deliberately held off taking any photos with the phone so that the "camera roll" folder wouldn't even be created. I discovered that whatever folder happens to be in THAT position, will randomly not display the thumbnails. Since I haven't taken any photos with the X, a folder named "Folders" sits in that corner. On a few occasions, the heading shows up, but no thumbnails until I change the phones orientation. So it's not the camera pictures folder specifically, it's whatever folder happens to sit in that spot.