I'm a former dev, and love finding little loopholes and bugs in stuff. The first time it happened, I didn't understand how it happened. The second and third was like... I think I got this, and know how to report it.
I had fun breaking it. Let's see if I can break it again. 馃榿
Replicable bug - In any mode, finish the game drawing all of the cards (achievable by boosting anti-busts. The program tries flipping over a blank card then fails the final count tasks. Should be a very easy fix. (If card stack = 0).