Increase the randomness in the card dealing. Far too often I've seen repeated dealing of Ace, 2, 3, 4, 5 coming out.
One far too many occasions I've been able to uncover Ace, 2, 3, 4, 5, 6 etc in a quick run of uncovering cards. This means that your dealing algorithm isn't random enough. I've played lots of solitaire card games and not come across this.