I am with Lloyds and had the same problem several times, spoke to Bc they said it was bank problem, check with bank and they said Bc are not fully using the new fraud prevention protocols that has been in place, today I passed this on to Bc and they said they don’t have to until April this year, hope this clears it up for you, I suggested they should have put this on their web site, but as usual I expect it has fallen on deaf ears