I have had really good luck with acf-50 and isopropyl.
I also love trying to fix things before it just gets put in the landfill.
Did the controller get wet by accident? Iirc sometimes when you turn those remote controls on they will use that to tell it that it’s in all neutral.
Have a real good look at the circuit board for anything burnt or popped.
Usually I would clean with iso we get the 99% stuff here at work. Then brush around with a tooth brush.
The iso will leave a white powered residue as well.
Then I will spray and soak it in acf-50 and brush around.
If it does it when you have the remote on and all knobs and trims to center then turn the car on. Try holding full righ on the controller.
Kids hey haha