Any of the Sony cameras that use SxS or XQD cards include a media check and media restore function that is designed to detect any problems with your recording media or the files stored on that media.
However the media check is only normally performed when you insert a card into the camera, it is not done when you eject a card as the camera never knows when you are about to do that.
So my advice is: When you want to remove the card to offload your footage ensure you have a green light next to the card, this means it should be safe to remove. Pop the card out as you would do normally but then re-insert the card and wait for the light to go from red, back to green. Check the LCD/VF for any messages, if there are no messages, take the card out and do your offload as normal.
Why? Every time you put an XQD or SxS card into the camera the card and files stored on it are checked for any signs of any issues. If there is a problem the camera will give you a “Restore Media” warning. If you see this warning always select OK and allow the camera to repair whatever the problem is. If you don’t restore the media and you then make a copy from the card, any copy you make will also be corrupt and the files may be inaccessible.
Once the files have been copied from the card it is no longer possible to restore the media. If there is a problem with the files on the card, the restore can only be done by the camera, before offload. So this simple check that takes just a few seconds can save a whole world of hurt. I wish there was a media check button you could press to force the check, but there isn’t. However this method works.
It’s also worth knowing that Catalyst Browse and the old Media Browser software performs a data integrity check if you directly attach an SxS card or XQD card to the computer and access the card from the software. If a problem is found you will get a message telling you to return the media to the camera and perform a media restore. But if this is some time after the shoot and you don’t have the camera to hand, this can be impossible. Which is why I like to check my media in the camera by re-inserting it back into the camera so that it gets checked for problems before the end of the shoot.