PSA - Purchasing craftables

I'd saved enough goblin gold to purchase 2 lots of the castle type walls. I purchased the first pack of 4 and started placing them. Once I had placed all 4 from that set, the tooltip suggested I could buy more for 540 goblin gold, so I placed a fifth wall but this time I was only given 1 wall for 540 gold!

Only purchase these packs from the crafting screen. I'll contact support to see if they'll do anything.