From a consumer perspective there's an unknown number of layers between your actions or instructions and what the backbone tech of the bank is doing, but having worked in the space I can point to a few things.

Firstly, the transaction failed and notified you about the error - that's certainly intentional.

Second, there's failures that would be invisible to you as the customer, such as "instead moving $100 from account A to account B it credited account B but didn't debit account A, without generating an error". Those are mostly the systems I'm talking about being insulated from AI development. Without more detail about the exact problem you had it's hard to tell if it's a failure in customer facing systems or backend infra.

Third, I'm assuming you were able to reach out to the bank directly and resolve the issue by talking to a person (if the issue was really outside the norm), which isn't something you can assume will be possible with a lot of customer service ops these days (or you're going to be waiting hours/days for that callback).

Fourth, you can't really know the error rate of the bank's systems, or how common a given particular error is. It may be a known issue, or it may be a completely unreported one. Assuming it's an error with something on the backend/backbone of the bank's operations, it's running code that can be inspected, reviewed, understood, and fixed - sometimes by a very expensive COBOL consultant.