I would share my own personal experiences of how to make an sucessfull update.
I myself has an Sony Bravia KDL-32WEE613, but as I suppose this is not only for this specific model.
But however as everybody knows how the general instructions are from Sony,but I myself has a different experience of it.
But before I describe this futher I also would explain the main differences between an Update and Clean Install
( factory reset).
Because however an Update just adds new features( it doen't remove anything of the already existing problem), but an Clean Install/ Factory Reset= Make an fresh/ clean installation.
So with this in mind, all what you have to to after each update ( via USB)- is to perform an Factory Reset.
Because however if you don't do it,you still will see your older/ previous firmware.
Even if you got an message of an sucessful update.