You re living in cloud cuckoo land if you think UB 'forgot' how to change the configurations in their system to pass on the ECB cuts.
They realised their error after, and only after, media coverage and a huge volume of calls and letters to the support team.
factual information here, ub rate increases and decreases are inputted manually into their systems but the system then amends all the rates on the mortgages automatically.
ub actually thought they had 30 days to decrease the rates from date of implementation by the ecb, they didnt read their own ts and cs. this was until it was noticed, due to it being noticed they amended their rates and backdated the decreases to the relevant dates.
it wasnt due to media coverage or due to complaints, it was due to someone checking the ts and cs and notifying the head guys in ub they got it wrong.