Some duplicate mortgage payments were mistakenly taken from customers during NatWest's IT meltdown, the bank's group has confirmed.
Royal Bank of Scotland (RBS) Group issued the latest in a series of apologies to customers and urged them to get in touch so it can put the problems right.
The group said it believes a "small number" of customers have been affected and promised that no one will be left permanently out of pocket.
A spokeswoman for RBS Group said: "We apologise to any customers experiencing problems today. We said last week that we expected to see a few bumps in the road for customers as we get things fully back on track.
"Any customers experiencing problems should contact our call centre or visit their local branch and we will put things right."
The group has been working "round the clock" to resolve the problems which began two weeks ago and meant NatWest, Ulster Bank and RBS customers' balances were not updating properly.
It has had greater difficulty clearing up the glitches, which meant people's wages did not appear and house purchases and holidays were disrupted, for Ulster Bank customers.