In California the law states any modification shall be modified based on the petitioners OSC...
Meaning if the father wishes to decrease his child support he must do so on his own OSC...
That was my experience which shows you the family court system is nothing but a scam and gets off on causing more and more conflict.
Oscar is my sons father however I fought three years to prevent ex husband (divorced for a year) from coming back to court to take custody of the child which a judgment was already in place for the natural father...
That place is just hell.