Light in main compartment doesn't turn on intermittenly

The lights in my refridgerator weren’t turning on frequently when I opened the door. I replaced the door light switch (Whirlpool Refrigerator Door Switch W11439253) and the light still doesn’t turn ocassionally although it occurs less frequently than before. To get it to work again, I have to push in the plunger and hold for 1 sec or 2 and then release it. Any idea what may be happening ?