As default configuration, the UV of Vcca/Vaux/Vcore will only assert FS0B, and no action on RSTB. In default state, FS0B is not released.
So, after start-up and before FS0B released, if a VAUX_UV occured, what's the action of FLT_Err?
As description on User Manual, it will incremented each time RSTB/FS0B is asserted. But if FS0B has been asserted or havn't been released, does it incremented?