Completely different scenarios.
The AIB top-up issue was in simple terms they increased the top-up by the amount of interest that was outstanding at the time, even though the interest wasn't due to be paid, so they lent more than the borrower had asked for. I'm assuming your 2,300 included compensation, but even then you would have been in the upper amounts involved. Most personal loan top-ups are for small amounts.
The mortgage issue discovered by UB was where the interest rate changed between offer date and drawdown. They were contractually entitled to apply the new rate, but didn't adequately inform the borrower.
The overcharge would be a factor of the balance and the amount rate had changed, so there won't be any small amounts involved. It was primarily fixed rates, so an average 2 year term that the customer was overcharged.