When trying to purchase the %-off skins an error may appear including "Error - We encountered an error handling your request. Give it another shot." Giving it another shot may work BUT not with "Slay Belle Katarina" (in my case). I think purchasing skins with this way doesn't work with legacy skins (legacy, because Slay Belle Katarina doesn't appear in the regular shop, even if not already purchased). I don't know if it's a bug or some temporary issue.