If the card is a class 10 as it appears I don’t think the card is the issue, unless you got a bad copy. Have you tried the camera with a different card, even if it’s the same kind, to see if that fixes it?
Here’s a long shot but if BOTH of the following are true – it MIGHT explain what’s going on:
* Have you installed Magic Lantern
* Are the clips longer than around 12 minutes?
If so, it probably has to do with the Magic Lantern and the way it gets around the standard Canon 12 minute / 4GB clip limit. Their wiki page says “you will lose a few seconds when a new file is created.”
Not sure what else it could be but others may have some ideas
Steve Crow