Congratulations! Erratic spoiler & battery power are OFTEN related. Bottom of my drivers seat heater went out & I still need to fix it, especially for when top is down in cool weather. Search here for water in lower trunk well issues, (locking control pump/module location). I think I dodged that bullet even with a detached rear window, but Coupes may leak too. I added 2 small drain holes, 1 in R. fender well, for insurance, (it might rain here again someday, probably a great flood).
Happy & Safe Motoring!