I'm using Microsoft mouse software with either a trackball or the Explorer 3 mouse. Sometimes, when I middle-click, instead of the new tab opening on button-up, it happens on button-down and button-up. Sometimes it happens twice on button-up. This means if I middle-click a link in chrome, I might get from 1-3 tabs opened. I can't figure out how to eliminate this behavior.
I am using a Microsoft IntelliMouse Explorer 3.0 on a 2014 MBP 15" running Yosemite 10.10.4. I'm running the intellipoint 8.2 drivers, and "mouse wheel click" is set to "Handled by Mac OS". At one point I was using USB overdrive, but I uninstalled it. Removing/inserting the mouse doesn't seem to help. The behavior is inconsistent – it seems to come and go in bursts.
Best Answer
@Tetsujin's comment was correct - this mouse was actually defective. It took a while to find one, but I compared to another identical model and didn't have the same problems.