Does that mean if a pax gets a penalty fare (could they get a criminal record??) through their card being declined and it's not their fault TSB will pay the fine? Seriously I hope common sense applies and staff simply take a record of the non-functioning card and the pax pays within a suitable time when they can.
It's unfortunate, I suppose, that many of us simply don't carry much cash around as we can use contactless or even our phones and we certainly don't go out assuming our cards won't function.
EDIT last night I only had pennies in actual cash around the house, so went to the pub using contactless payment on the bus to there, and hit a cash machine near the pub to get the money for the pint! Might not have been allowed on the bus if the card failed behind my back!