Washer # 18, Drain Flow Plug 1.8 gpm for Sears, North Star, and GE residential water softeners.
Part Number 0501228 or GE # WS03X10022 ( Plug, Flow, Rinse Control ).
This flow plug can get a chunk of debris lodged in it,
or if the water is highly chlorinated, it can become swollen and partially shut.
Both would have the effect of restricting the flow rate out the drain, and this can cause lack of suction in the Brine Rinse cycle.