Version: 54.0.2794.0
OS: repro on Windows, but any (incl. ChromeOS), I think

What steps will reproduce the problem?
(1) Have ChromeVox extension installed and in ChromeVoxNext mode.
(2) Disable ChromeVox extension at chrome://extensions
(3) Open new tab, load some page with a text box, e.g. http://www.deque.com/padam/demo-accessible-client-side-form-validation-with-html5.html
(4) Focus some text field
(5) Switch back to chrome://extensions tab
(6) Activate ChromeVox extension
(7) Switch back to your content tab (e.g. by Ctrl+T)
(8) Type letter into the text field without refocusing it by clicking / tab

What is the expected output?

Pressed letter is uttered by ChromeVoxNext

What do you see instead?

ChromeVoxNext is silent. Second and following letters are read out.