No financial institution is immune from having a technical issue. The real test is how quickly a financial institution can identify and recover to make things right when they do have an issue. This could have been a BoA issue, could of been a Zelle issue or a combination of both BoA and Zelle. Insiders know the dirty details but those details are generally not publicized.
News said that Zelle is owned by B of A & 5 other banks.