[Bug] Stacked bar chart: items stay faded after hover

### Version

6.0.0, 5.6.0, 5.4.3

### Link to Minimal Reproduction

https://codepen.io/corasla/pen/gbPLgWg

### Steps to Reproduce

1. Open the stacked bar chart in the reproduction link.
2. Hover over individual items in the stacked bars.

3. Observe that:
- Similar items are highlighted as expected.
- Some hovered items become semi-transparent after hover ends and never return to full opacity.

### Current Behavior

- After hovering out, some of the previously hovered items remain gray/transparent.
- This effect accumulates as you hover more items.
- Only a full page refresh resets their appearance

### Expected Behavior

- While hovering: similar items should be highlighted, non-similar items should be faded.
- After hovering ends: all items should restore their original color and opacity (100%).

### Environment

```markdown
- OS: macOS, Windows 11 (also reproducible on others)
- Browser: Chrome (latest, reproducible across versions)
- Framework: independent of framework (tested standalone and with frameworks)
```

### Any additional comments?

- This issue occurs with larger datasets (see reproduction).
- With small datasets, the problem does not appear.