if all three banks have the same parent bank they can settle all transactions at the end of last. but this is speculations, we don't have detals. 
a few years ago hryvna was very volatile, (I live in Ukraine), and I bought something in EU online shop with my ukranian card. and transaction looked immediate, money left my card, shop received their money. but then like week later my card was charged something like 0.5 euro or something. I called my bank and they said you know that transaction settled 4 days later and by this moment euro/uah rate changed so we charged difference