I encounter this issue all the time in regular games and traphase, today's boss just reminded me of it again.
I'm on PC and I use mouse to drag and cast cards.
So, if there are too many cards, you click on one, then drag it up to cast it, but if you move a tiny bit left or right then the card changes to the adjacent one while it is in the process of being pulled.
That is super annoying - it literally is challenging a bit to cast the right card when there are 10 or more of them and they are very close to each other. I think in all card games, if you click on a card and hold it, then the card should remain 'grabbed' even if you hover cursor over another card. Or we could have some new way to scroll through cards in hand one by one.