Onceyou get the license lights removed, an endoscope will be helpful in looking around to see what's going on. I strongly recommend the Autel endoscope, available from Amazon at about $55 - don't buy the asian "bargain" endoscopes.
What do you feel when you operate the release lever on the trunk lid? Does it move with little or no resistance in its full range of motion, or does it stop part way, as if it has hit a brick wall?