When your FICO is computed the program tells the credit bureau what the 4 most important factors were in determining the score. Fair, Isaac and the credit bureaus do not want to reveal how these scores are computed. The score is only as good as the data. The amount of credit data history is so large that there are problems with it. The most common problem that I see is with relatives with the same name.
Borrowers often dispute the data but it is very accurate.
It will become more important that ever to keep a good or perfect credit history. The downpayment must be well-documented. That is, you must show, for example, bank statements proving that you have had the money for at least 2 months. The purpose of all this is to make sure that the downpayment is not a loan and most especially not coming from the seller. The mortgage insurance also depends on the loan amount and the type of loan.