In the winter I noticed this happening a lot when doing hours of practicing.
My working theory is that the moisture in your hands, and in the air, gets absorbed into the edges of the cards. The cards swell around the perimeter, but not so much in the centers. This uneven expansion is the cause.
And, basically all of the various tips on how to fix them boil down to the same negative the orientation of the cards, or leave them alone for a while.
I just ended up ordering a brick of Bees to practice with and save the good cards for performing. When a deck starts clicking, just switch decks.
Encourages card collecting too...