Thanks so much for making this! Just putting a couple bugs on your radar:
Somewhere around World 4, I started getting a Pig card where the Weapon card should be. The Pig card would show in my deck in the Weapon Cards section in the "View Deck" view, but when I would go into the shop, it wasn't there (so I couldn't sell it).
In previous rounds of this same save, the game would also spawn a weapon card that I'd sold many rounds ago. Even though I was buying new ones, it would never spawn those weapon cards, just the old card that wasn't even in my deck anymore.