[Bigginge1976]

After I have transferred my photos to my laptop from the SD card & put the card back into the camera I get the error message "Unable to display image" on some of the photos, the photos are still on the card (I've checked by putting card back in the laptop) but, the in camera gallery doesn't display them.
The firmware is upto date, I have tried a few different cards, all of which have been formatted both in the camera and on the Laptop before use, it affects both jpeg and DNG.
KS-2
Sandisk 16Gb and 32Gb cards
Any suggestions?

[35mmfilmfan]

If you are using the laptop's built-in card reader, be sure to set write protect before inserting the card. Once images have been successfully transferred, use the 'Eject' function to dismount the card prior to removing it. Do not forget to remove write protect before replacing the card in the camera. The reason is that Windows can write 'hidden' files to the card, which the camera cannot read. If you are sure all images have been transferred from the card successfully, it may be time to reformat the card, either in the camera or using SDFormatter (free) on your laptop.

Good luck

[Bigginge1976]

If you are using the laptop's built-in card reader, be sure to set write protect before inserting the card. Once images have been successfully transferred, use the 'Eject' function to dismount the card prior to removing it. Do not forget to remove write protect before replacing the card in the camera. The reason is that Windows can write 'hidden' files to the card, which the camera cannot read. If you are sure all images have been transferred from the card successfully, it may be time to reformat the card, either in the camera or using SDFormatter (free) on your laptop.

Good luck

Thanks for that, I'll give that a try next time 👍

[kypfer]

Not only "that Windows can write 'hidden' files to the card", which shouldn't affect the card's performance in the camera as the camera usually just ignores files it isn't interested in, but some software will actually edit the EXIF information of any image file it can get it's claws into, so the camera no longer recognises the file(s) as something it has written and will refuse to deal with them!
This arrogance by the software manufacturers that leaves the files effectively partially corrupt and not totally fit-for-purpose is probably wider spread than many realise!
Write-protecting the card will save the files on the card in the first instance, but if the card ever gets emptied or formatted or totally deleted for re-use, rather than just allocated to an archive, it could mean that there isn't an "un-corrupted" version of any file available!

[35mmfilmfan]

Thanks for that clarification @kypfer.

The only software that touches the images on the actual card in my PC is Windows File Explorer, which I use to copy the files to their destination. Once done, I eject the card prior to using any processing software - just in case !

[AfterPentax Mark II]

If you have this problem with all the cards you tried it with as you wrote, then it must be malfunctioning of the camera. Always format in the camera, never on the computer unless you use SDFormatter. Have a look at this exchange as well: https://www.pentaxforums.com/forums/190-pentax-k-1-k-1-ii/429597-k1-file-issue.html#post5375184

[Not a Number]

The culprit is the hidden System Volume Information folder Windows indexing creates. If you disable indexing (disable the service) Windows won't create the folder.

Or you can set Windows not to index removable drives:
Prevent System Volume Information folder creation on USB

Once the service or removable drive indexing is disabled you should be able to remove the hidden folder without formatting the card. There are plenty of tutorials and blogs to step you through deleting the folder.

[kypfer]

Thanks for that clarification @kypfer.

The only software that touches the images on the actual card in my PC is Windows File Explorer, which I use to copy the files to their destination. Once done, I eject the card prior to using any processing software - just in case !

Windows Explorer may be all it takes, if the "background settings" are configured appropriately.
As with music files and other media, if Windows is given the opportunity it can try to add any appropriate file it can find to various indexes for "search" purposes (and possible data harvesting, GPS locations or whatever) and part of this procedure can be to modify the EXIF so's it knows not to bother a second time.
I strongly suspect, but never finally bothered to prove, that Google's "Picasa" and probably some of Adobe's offerings perform a similar function, sitting permanently loaded quietly in the background as a 'plug-in', 'add-on' or 'background service', automatically activating whenever an appropriate file became available!
I do know I had many months worth of image files "infected" like this when I was doing some software comparison tests many years ago, some were recoverable from archive, others were permanently damaged unless the EXIF data was manually edited on a file-by-file basis!

[35mmfilmfan]

Thanks again, @kypfer and @Not A Number for this helpful additional information. I have Windows Indexing turned off on all drives, and as mentioned earlier, I set write-protect before inserting the card. So far (touch wood !) these precautions have been successful, in over seven years of using Pentax DSLRs.