When you set the banner image on a user or group profile, the image upload UI gives you option to crop the image (which is especially useful for banner images, which aren't a normal image aspect ratio), but however you crop the image, the actual displayed banner image is just the top of the whole uncropped image.
[Edit] OK, the actual problem seems to be that if you set the banner image once and then set it again, using a file with the same filename then the UI continues to display the old file. Maybe its a caching issue?
When you set the banner image on a user or group profile, the image upload UI gives you option to crop the image (which is especially useful for banner images, which aren't a normal image aspect ratio), but however you crop the image, the actual displayed banner image is just the top of the whole uncropped image.
[Edit] OK, the actual problem seems to be that if you set the banner image once and then set it again, using a file with the same filename then the UI continues to display the old file. Maybe its a caching issue?