Looks like a simple UI issue, no biggie. They are used to way worse, and barely recoverable, issues created by people without a clue. Horrible sector to work in.
In Austria I only see cash being exchanged at the supermarket and when I see someone paying by card or, God forbid, phone or watch, it's most likely a foreigner form another country where cash payments are not popular rather than a local who went cashless.
Here's an example reporting on an IT failure at a British bank: https://home.barclays/content/dam/home-barclays/documents/ci...
Current balance: -1,000,000.
Debit: Spent money at Koenigsegg (a Swedish car brand), new balance: -1 billion.
Patch: flip - to +: new balance: 1 billion
People tried buying things and had their purchases denied.
Some long-standing accounts received very large cheques (it was the 90s, so yes, cheques).
The FI gave the customers the choice to either return the cheques or have future interest payments withheld. Surprisingly the vast majority simply returned the cheques.
We had to write additional code to clawback the interest on the other accounts. I doubt if the FI would have had any recourse if people had just closed their accounts and kept the cheque but to the best of my knowledge nobody did.