I wanted to share this with everyone now that I discovered this issue. I was working on having the common rust hole that occurs around the third row seat mount above the rear passenger side wheel well repaired. When I was reinstalling all the interior plastic panels over that wheel well I saw a fair amount of moisture inside. We had a rain storm the prior night. I begain to examine the cargo door seal and noticed it was pulling away from the sheet metal in the upper right corner and the opening was filled with debris. I was able to easily pull the weatherstrip off. Once it was off I saw a fair amount of corrosion on the sheet metal lip that was under the weatherstrip (see photos). The weatherstrip slot that installs over the sheet metal lip was flaring around the comer locations. The seal was also very crunchy when I flexed it. It turns out it has metal inside it that appears to improve the seal. Those seals are very expensive so I took a chnace and ordered it from Rukn Al Injaz Auto Spare Parts TR. LLC. The cost was $125 plus shipping which is far less than other sources at around $275. The weatherstrip arrived and appeared to be a correct Toyota part (see photo). I sanded off the rust with 60 grit sandpaper, treated the areas with POR-15 and then painted the POR-15 with Duplicolor HWP101 Silver. The new seal comes with a greasy substance inside the recess that gets pushed over the sheet metal lip. This substance matched substance I removed when I took the old seal off. I cut the old seal open to see what was going on inside it. There was severely rusted metal inside it (see photo). The repair worked great and the seal is excellent.
