Also...a side note. The agent who helped to refund the tickets and I discussed the oddity that earlier I could not complete the purchase on Delta.com. We surmised that FlightHub had already created the DL PNR and the unknown error that the DL systems were giving were because it saw me trying to buy duplicate tickets. We won't know for sure, but I'm highly suspect this was the case. Also to add to this speculation...while the 9 tickets failed (and I also tried 8, 7, 6, 5 tickets instead but with same names), I was able to buy the same itinerary for myself and wife with no error at all (so that we would be eligible for comp upgrades as only 2 travelers).

Just an interesting data point.