rear area cargo light.

[Ldub]

Same with mine. Maybe an extra layer of tape between the ridges on the trim panel to even out the surface would help?

Yep, I doubled the thickness of the tape in the appropriate area to follow the contour of the ridges, it was more a problem with the double stick that came with the light being of inferior quality.
Since then, I've replaced it with 3M HD doublestick, it's had no further problems.