I have a Nikon D3300. An error message started to intermittently appear, stating that the SD card was damaged. A new card would work for a while, but then the same message. I have found that if you insert the card, and put a small piece of paper behind the card wile closing the card door it work fine. The cards seems to need to be push in a little deeper into the slot for some reason. There it obviously a contact issue with the card slot. Any thoughts? Thank you, Pat