This is also happening on other areas of wikipedia that aren't parentheses specific and might just be related to how links are handled? Here is another example without parens but showing a similar behavior of getting stuck in one spot and then lagging behind a bit.

https://en.wikipedia.org/wiki/Australosphenida

Invoke feature on this text:
Monotremata, divided into the families Ornithorhynchidae (platypus), Steropodontidae and Tachyglossidae (echidnas) and the genus Kryoryctes

Another page with similar problems is https://en.wikipedia.org/wiki/Mammal - the first paragraph shows the focus ring moving very far away, a dramatic difference. 

More specific repro steps: this happens with some mix of parens and nodes. It doesn't happen on the string "its family (Ornithorhynchidae) and genus (Ornithorhynchus)" by itself, but requires the combination of links and parens to occur.

That reduces the priority / impact.

Please let me know how differentiate between nodes and parens for testing purposes. Thanks!

In this case I'm comparing between links, italics, bold text, and other formatting to text. Each time formatting changes, the accessibility tree actually has a new staticText/inlineTextBox node. So if you have <b>one</b><i>two</i>, that looks like "one two", but each is it's own node in the tree. Similarly with inline images, buttons, etc. Does that make sense?

Here's the smallest repro I could come up with for parens:

data:text/html,<b>one</b>(<i>two</i>)

In this case there are 4 staticText nodes:
one
(
two
)

So STS is getting tripped up at the open paren.

If the page was instead,
data:text/html,<b>one</b> a</i>two</i>
Highlighting works properly.

This issue is because the paren is not vocalized.

This bug requires a change to TTS to be completely fixed.