I have the single piece. Mine doesn't do that but suffers from chronic sagging, around the trunk keyhole section.
its held on by lots of double-sided tape, and over time, i guess it loses its holding strength. no sag for me, the POS shop I went to ended up using lots of epoxy to hold it on
Yeah mine always puddles on the drivers side. Does your wing sit crooked? Mine as well as a friends both side kind of sideways on the car.. the driver side of the brakelight is higher than the passenger side.