I have one teacher whose Safari isn't showing the scrollbars (both horizontal and vertical) in their gradebook. They can still use mouse gestures to scroll in both directions, and when they do, the scrollbars appear momentarily, but then they disappear. We've checked his system settings, and he has it set so that scrollbars should always be visible everywhere. If he goes into Firefox, he sees the scrollbars.
When I go into his course on my Safari, I see the scrollbars. I'm pretty sure it's something he installed on his computer. He checked for browser Extensions, and there are none.
Is there anything else I could look at that might help explain why Safari isn't showing scrollbars?