If you don't see your card it means the card is broken on the site. I have found vp cards have a big chance of not being in the print pdf.
That's strange. I've not seen that with the many Traditional cards I've entered in tens of decks. So, as you say, it may be a problem exclusive to sume subset of sets. (But on the other hand -- I've never tries to print only 1 or a few cards as PDF -- always half or whole decks.)
Do you have examples of such cards? I'm sure whomever it concerns will ask for them.
I have seen -- once or twice -- problems with, seemingly, very specific arrangements of decks; one or more cards are then "represented" by a stretched image of a deck category text box. This is "solved" by NOT printing the deck list along with the card images -- but print each of those two option as a separate PDF.
I've not found it worth noting, but perhaps I should've done so earlier.
Now there's two puzzles to solve!