The CAN bus window motors have been known to go bad in general. Mine went bad on my car. Of course it is a different car than yours but they both have CAN bus. The dealer can diagnose it with their computers, but a new regulator out of a junk yard might be cheaper. The fact that your switch only works sometimes suggests a fault with the motor/module (one piece).

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra