I have thirty years experience in the IT industry and have worked in most of the large banks in Europe.
Each and every one of them has invested enormous amounts of money, time and energy in their IT infrastructures.
Some of these systems have been very intelligently put together - in some cases I would describe them as being ingenious. They are surrounded by layers of change management, change control and rigorous testing.
They really are very highly-engineered tightly-controlled environments.
They have all failed multiple times over their lifetimes.
Even the core of the mainframe operating system has fixes which are regularly supplied by IBM.
I'd prefer to be flown by a sentient being, despite the fact that it is sentient beings responsible for the above failures.