Mine is a zipped card wallet so not quite the same.
As you say, it's normal. The leather gives over the time and it will happen. Most important thing is not to lose those cards.
You could try 2 cards in together to prolong its usefulness.
View attachment 4304419 View attachment 4304419 View attachment 4304420 I just had to post pics. Because she is so adorable. It’s really only the first slot that’s lose. If I just use the last 3 I might get another year out of her.