SourceTree handles wheel mouse scrolling incorrectly. Rather than scrolling down, it scrolls up, and vice versa.
For example, in the Log/History view, if I scroll down my wheel mouse, this causes the window to scroll up.
If I scroll up with my mouse, the window scrolls down. This is the opposite of what should be happening.

This is happening only if the Control Panel > Mouse > Wheel is set to "One screen at a time" (instead of scrolling a particular number of lines)