I can confirm that ChromeVox is crashing and relaunching itself after some time. 

I believe it is related to  bug 888566  since it also shows the behavior where all keypresses are doubled - that's why ChromeVox is turning itself back on again after trying to turn it off - the keypresses are doubled. 

If I go to chrome://inspect and inspect the ChromeVox extension while it crashes and relaunches itself, I get the following errors and logs during the time it is down through when it came back up:

Failed to load resource: net::ERR_FILE_NOT_FOUND
deps.js:1 Failed to load resource: net::ERR_FILE_NOT_FOUND
loader.js:1 Failed to load resource: net::ERR_FILE_NOT_FOUND
chromeVox2ChromeBackgroundScript.js:977 [Deprecation] Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
cvox.KeyMap.readJSON_ @ chromeVox2ChromeBackgroundScript.js:977
chromeVox2ChromeBackgroundScript.js:612 The Web Audio autoplay policy will be re-enabled in Chrome 70 (October 2018). Please check that your website is compatible with it. https://goo.gl/7K7WLu
EarconEngine @ chromeVox2ChromeBackgroundScript.js:612
43chrome-extension://invalid/:1 Failed to load resource: net::ERR_FAILED
2chromeVox2ChromeBackgroundScript.js:1159 Speak (C) category=nav "Inspect with Chrome Developer Tools"
chromeVox2ChromeBackgroundScript.js:648 loaded liblouis Native Client instance
chromeVox2ChromeBackgroundScript.js:1823 Injecting into 469985194 Object
chromeVox2ChromeBackgroundScript.js:1823 Injecting into 469985195 Object
chromeVox2ChromeBackgroundScript.js:1823 Injecting into 469985234 Object
chromeVox2ChromeBackgroundScript.js:1823 Injecting into 469985237 Object
chromeVox2ChromeBackgroundScript.js:1823 Injecting into 469985236 Object
2chromeVox2ChromeBackgroundScript.js:785 Missing role info for unknown
(anonymous) @ chromeVox2ChromeBackgroundScript.js:785
chromeVox2ChromeBackgroundScript.js:1159 Speak (C) category=nav "unknown"
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav " - leberly@chromium.org, window"
chromeVox2ChromeBackgroundScript.js:1159 Speak (C) category=nav "inspect"
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav "Inspect with Chrome Developer Tools"
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav "Inspect with Chrome Developer Tools - Google Chrome - leberly@chromium.org, window"
2chromeVox2ChromeBackgroundScript.js:1159 Speak (C) category=nav "chrome-devtools://devtools/bundled/devtools_app.html?dockSide=undocked"
chromeVox2ChromeBackgroundScript.js:1159 Speak (C) category=nav "Code editor"
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav ""
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav "Text area"
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav "is editing"
chromeVox2ChromeBackgroundScript.js:1159 Speak (Q) category=nav "Use Search Left or Right for Home or End, Search Control Left or Right for Control Home or End, Search Up or Down for Page Up or Down."

Google Chrome	70.0.3538.41 (Official Build) beta (64-bit)
Firmware Version	Google_Eve.9584.160.0


Following the above steps with ChromeVox on, upon putting focus into the text box and pressing enter ALL of Chrome crashes, not just ChromeVox. After a second or so ChromeVox recovers and Chrome goes back to the NTP with the "restore" dialog indicating that a crash had occurred. 

However, nothing appears in chrome://crashes. 


Summary:
M68: no problems
M69: ChromeVox crashes after pressing enter in the text box
M70: All of Chrome crashes after pressing enter in the text box
M71: no problems 

Just to the extra through, I tested M71 on the same hardware as the other tests, Eve. No problems. 
Chrome 71.0.3567.0 (Official Build) dev (64-bit)
Google_Eve.9584.171.0

@leberly, could you get a crash log via chrome://crash.

If the stack trace looks like the one in 
https://bugs.chromium.org/p/chromium/issues/detail?id=888566

please dup this bug to the above one.

Looks like no crash log available. I'll take a closer look when I'm back from traveling.

That's right, no crash log after several attempts to trigger one. I'll wait to dupe this bug until you look at it closer. 

This should be a dup of
https://bugs.chromium.org/p/chromium/issues/detail?id=888566&q=commentby%3Ame%20component%3AUI%3EAccessibility%3EChromeVox%20%20crash&colspec=ID%20Pri%20M%20Stars%20ReleaseBlock%20Component%20Status%20Owner%20Summary%20OS%20Modified

Please verify and resolve this bug accordingly. Thanks!