Unified diff scrolling is buggy when using the trackpad

Unified diff scrolling frequently:

• doesn't scroll at all,
• scrolls a small distance, then jumps back to its original position,
• scrolls horizontally when I'm only scrolling vertically, or
• scrolls in the opposite direction.

This happens to me dozens of times a week. Refreshing the page usually fixes it, but not always. I use Chrome; let me know if there's any other information I can give to help diagnose the problems.