If youíve pinpointed a small leak one option is to try a flowable sealer.
Iíve used the Permatex sealer with some success on the wing windows on my í72. Sealants : Permatexģ Flowable Silicone Windshield & Glass Sealer
The data sheets donít indicate acetic acid as a vehicle so it seems to be safe for aluminum.
I used Vulcum to seal the corners on my í67 where the channel had shrunk. Maybe a combination of the Prematex to seep into the joint. Then Sikaflex or Parbond to build up gap.
Depending on how severe the leak is it might be a better option than removing the window and frame.