UB aren't perfect by any means. I've had a lot of problems with them down through the years, mainly due to individual staff members incompetence. At various times they took funds from the incorrect account (despite being given instructions to take it from another), leaving me with no cash. Another time they wanted to cancel my bank card whilst I was travelling and said they would issue one within a month to my parents who could then post it out to me (!!)
Reckon it can happen at any bank whether it be AIB, UB or BoI. Everyone's experience is different