It's crazy. My main account is with Starling and I have a Lloyds account for a saving an account and some free cinema tickets. I don't think I've ever had an issue with Starling, it's great - Lloyds fails to sign in about 50% of the time consistently.
Do you have an account with Llyods though?
Strange. My Lloyds login has never failed since I opened the account 11 years ago.
The usability of their mobile app is atrocious though. Good thing they have a website.