I've already filed a ticket on this. Not sure if it really is a bug exactly. Just now I decided to vend at Prize Get and vended a total of 26 items, 2 of which were from Magic Box and Defend and Conquer respectively.

[item2=20HP Healing Potion]

[item2=Kumos Helmet]

[item2=Illumis Spectrum Shield] *most recent unrelated items

[item2=Spiked Montre Tailguard]

[item2=10HP Healing Potion]

[item2=Angelic Rod]

[item2=Devonti Crystal]

This is what I've gotten so far, the rest are plushies/beanbags/toys. Thank you