Leaking gutter down pipe/elbow junction
When mine leaked from a similar location, it was from the screw. Typically, they use self-tapping screws to hold the pieces together. Since this is just thin aluminum, the interior piece gets pushed up as the screw taps through, and/or it leaves a jagged piece so water can get out.
All I did to fix it was to smear the bottom surface of the upper pipe with a generous glob of silicone caulk, slide it in, and replace the screw again.