In the Series _.srs) file there are entries for Full Course Yellow.
Try adjusting the following lines to what's pictured below;
// Minimum laps during a full-course yellow; default = 2, possible values are 1 (?) and up ... remember that it
// might be useful to override this one in some track GDBs.
MinimumYellowLaps = 1
// Additional random yellow laps; default = 1, possible values are 0 and up.
RandomYellowLaps = 0
And check your track .gdb file to ensure FCY is not specified there.