Test your mouse scroll wheel for unwanted reverse scrolling.
Hover over a box and scroll in the arrow's direction. The box pulses green for correct scrolls. If your scroll wheel registers the opposite direction, it is likely faulty. The box will turn red to indicate a detected fault and divide the number of faulty scrolls by the total scrolls to calculate the failure rate.
Failure rate is the share of scrolls that came out backwards: 99 good scrolls and 1 bad one is a 1% failure rate. A healthy wheel sits at 0%. Any sustained reading above 0% suggests the encoder needs cleaning or replacement. The failure rate is only an estimation and isn't truly diagnostic, but there to indicate the prevalence of faulty scrolls.
Keep counting after a faulty scroll: by default the box locks red on the first fault. Enable this toggle to keep the box live so you can rack up hundreds of scrolls on a flaky wheel and converge on a precise failure rate.