I made many LU journeys in Z1-4 and one costing 1.40 to Z5.
I was charged 14.40, rather than 12.00 - the Z1-4 cap + 1.40.
Oyster helpdesk staff took a few days to agree that I had been
overcharged and agreed an ex gratia payment for the inconvenience.
The payments were delayed for an extra day as they needed "approval".
Automatic overpayment detection does not recognise the situation.

OTOH, there are discrepancies between the Single Fare Finder and Oyster.
(Oyster charges less.)
Moorgate - Queens Road Peckham peak shows as 3.80 but charges 3.70.
It seems there were recent changes to charges between LU & NR.
The Single Fare Finder has not been updated to reflect those changes.
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Walter Briscoe