Ohhh, I see, thanks for reporting this! That's very kind of you to offer a video of the bug, I appreciate that a lot. That's also great to hear you still kept playing despite the crashes and progress loss :)
I found the cause - it happens if you try to swap a card with the void (so press left arrow key while hovering your first card, or right arrow key while hovering your last card).
That's so annoying because I specifically added guard rails to prevent that, but at the last minute I added the ability to use A and D to reorder the cards as well, so the code became:
if pressed left arrow or pressed A and not first card {swap cards}
but I didn't add any brackets, so the guard rail now only applies if you press A. Definitely a lesson in not throwing features in last minute, that could have been a lot worse!
Out of curiosity, what aesthetic function did the magnifying glass appear to be? Perhaps I need to change the icon on that if it could be misconstrued as decorative!