I worked for them. I’ve seen their list of error code reasons. Literally one of the error codes you could get was labelled as ‘WTF happened?’ on the list.
‘Too many buckets’ was another one, that one made me laugh tbh.
But they literally have like a 12+ page document of error codes and what they mean. The system is pretty buggy.
But generally our solution was, clear cache and cookies or try a different browser. It 75% of the time worked. If that didn’t work, customer service could remove cards for you.