First of all, the body shop should be responsible to fix this since they last touched it. Did they actually remove the hatch trim from under and completely remove the spoiler assembly? Or did they just spray everything installed on the car? When the spoiler is raised the exposed portion of the spoiler assembly was never painted from the factory (when the spoiler is completely raised)

If it is the spoiler high limit switch, that is discontinued and nobody has found a replacement that I am aware of. Your best bet will probably be to buy a complete used spoiler assembly from eBay and hope it is functional and completely replace what you have.

Download the service manual and do the troubleshooting is another option. You can remove the inside hatch trim while the hatch is raised and see if anything looks out of place or loose plugs etc.

It is a tough one, good luck.