Tell your "mechanic" to be a MECHANIC - the wing that keeps going up when it shouldn't is an electronic issue. But in YOUR case, you are describing what certainly sounds like a mechanical issue.
Have him look for physical reason(s) the wing can't go up. If he finds none, I'd suspect the "upper" limit switch is closing before the wing gets to full extension.

He can verity limit switch operation with a simple pocket voltmeter, the limit switch closes, and applies a ground to the BCM, when the wing gets to full extension. If that line is going to ground as the wing stops moving, it is because the limit switch is closing before it should. Refer him to the diagrams in the service manual.