Sure, that area that is missing caulk could be the cause of your leak. Then again, when water enters a structure it can travel along any framing members from above and exit in the interior in a different location.
I have a lot of time invested in my rig so I do a pressurized leak test every year. It is easy to do and i have a squirrel cage blower that is just right for the pressures needed. IIRC, the commercial Sealtech testing is around $100 but may be a bit more. I do know that an undiscovered leak that's allowed to continue and cause framing damage is a LOT more.
