This seems like an absolute disaster:
The very short version is that a UK bank, TSB, which had been merged into and then many years later was spun out of Lloyds Bank, was bought by the Spanish bank Banco Sabadell in 2015. Lloyds had continued to run the TSB systems and was to transfer them over to Sabadell over the weekend. It's turned out to be an epic failure, and it's not clear if and when this can be straightened out.
It is bad enough that bank IT problem had been so severe and protracted a major newspaper, The Guardian, created a live blog for it that has now been running for two days.
The more serious issue is the fact that customers still can't access online accounts and even more disconcerting, are sometimes being allowed into other people's accounts, says there are massive problems with data integrity. That's a nightmare to sort out.
Even worse, the fact that this situation has persisted strongly suggests that Lloyds went ahead with the migration without allowing for a rollback.
This seems to be a mistake, and not enemy action.