It uses some kind of JS trick to replace usernames and passwords with asterisks, and you end up with all kinds of invalid information stored in your password manager.
I currently use BitWarden (LastPass previously) and neither have had a problem logging into Citi's website though it's been quite some time since I tried to add a new entry from their site.
+1 for BitWarden. For anyone reading this unfamiliar, it's an open source password manager with all the usual features (including iOS Fingerprint enabled client etc, shared group passwords), but the server is also open-source, and you can host your vault on your own server. It's free for individuals/families, supported by Enterprise licensing (or you can roll your own).
I would think the fix to this would be manually entering the credentials into the password manager rather than having it read the credentials from the site.