I didn't know what it was so I clicked a few buttons in the app and the money was back instantly.
That was on Commerzbank. Dunno if others are the same!
So they send a polite email informing you of it and you pay it a few days late?
No reasonable entity would charge late fees as that's a great way to anger otherwise perfect customers?
For me to personally end up in this situation the bank would need to somehow SEPA out like 2 years worth of mortgages at once in a short timeframe, which is not a realistic scenario.
Also: it takes A LOT of letters and court orders for them to cut your utilities. I'm not joking, it's more than a couple of Mahnungs, then it goes to debt collection, then it goes to court. The court will then take the money out of your account.
That's all before power gets cut.
It definitely won't be because of a single missed payment.
Even in the situation above: if your in-laws somehow had no balance "at once on day x" because of a fake SEPA, they would be able to reverse via app, or go to the bank and reverse.