As to why that would occur for the same applicant, it could be that in the second round of the application, the visa officer had some questions about the source, the stability, or possibly the legal ownership of the funds.
You need to know that we have a significant degree of fraud in our processes. It's endemic. Lots of folks invent banking statements that, when we go to check them out, turn out to be fraudulent. Off the top of my head, those are the kinds of issues that I think might come to a visa officer's attention.