2 things - the first is not such a big deal but thought it was worth mentioning:
1 - When the puzzle is first generated, after the picture loads onto the elements, the puzzle pieces are suspended in the air until you interact with them, and then they will fall to the table.
2 - Here's the major thing. I was using a bag to sort the pieces, and when I pulled a piece out, it was locked in place above the bag. I was able to unlock it and afterwards when you left-click to grab it, it gets stuck to the finger pointer. When you left-click again, it appears to have lost its collision detection - it fell through the table, and eventually it goes through the world, resulting in a notification on screen that the piece was destroyed, rendering the puzzle incomplete due to missing a piece. Bug is consistent with 100% reproduction rate, and occurs on all puzzle sizes.