I'm not sure how else to describe it.

Reproduction:

1. Have a factory.
2. Mouseover any of the categories on the left.
3. Unpause the game, if not already.
4. Wait for the pie chart to update.
5. The highlighted segment will be moved next to "Other", as pictured... rather than deleted or resized? Also, the highlighted entry on the left will no longer be highlighted.
6. For extra fun, pause the game with a keybind, then remove the cursor from the category on the left (or to another category). The "ghost" highlight segment on the pie chart will disappear immediately.

Does not work on the Production tab (on my save), that appears to be because of the absence of the "Other" category. The update still kills the highlight, though, making the highlight only usable while the game is paused.

Also works on Workers tab (pie chart under "Top consumers") and the Maintenance pie charts... if they have the Other category, else they behave like my Production tab, and only remove the highlight.

Might theoretically work on the computing pie charts... but I have only one producer/consumer on those, so I obviously don't see the critical Other category.

Update 4.1 | v0.8.4a (b588). I seem to remember it working fine (as in, the way you would expect it to, not this way) on an earlier version.