Trackpad vertical scrolling reversed in latest update

Since updating to 10.10.2 a few days ago, my trackpad scrolling is reversed in the vertical direction only.

• Toggling the "Scroll direction: natural" checkbox in system preferences does fix the issue, but causes horizontal scrolling and all the forward/back two-finger gestures to be reversed.
• Note that the video that plays in the trackpad preferences is now incorrect; if I follow the video's motion, the reverse effect happens (since the update).
• I see this issue in a wide variety of applications, including Safari, the System Preferences dialog, Terminal, etc.
• I have tried toggling this button many times and restarting, to no avail.

This is extremely frustrating, as I must choose between either having reversed vertical scrolling or reversed horizontal/gestures, neither of which are comfortable.