Seems like I saw something about this elsewhere recently too but I don't remember where. I feed BG, but the cases I am feeding from were purchased last September. However, I am now remembering that I did have some trouble last summer with cases being delivered with the tops of the cans being unsealed. I think there was a problem with that, because the next shipment I got, in September, the style of the can and lids has been changed.
What's the numbers and dates on your cans?
Here's a lot number from one of the cases (turkey it was) where the lids had come unsealed:
Best by 11 JUN 13
11162 CL2 20474 0953
I happened to have a can saved from then. I don't have any of the others. I got my money back from the place I purchased them, at the time.