Stuck screws on shift actuator

I cannot loosen the two green screws that hold in place the shift actuator on my Maytag Centennial washer, Model No. MVWC360AW0. (The machine looks like the MVWB765W at the head of this thread.) Here is a screenshot from a YouTube video:

I have tried for hours to loosen these screws with a Phillips screwdriver. I have sprayed them with WD-40. They won't budge.

All the YouTube videos show these screws turning easily.

Does anyone know how to get these two screws to turn?

I was able to remove these two screws by using valve-grinding compound. The screws were rusty.