Magento2.2 Unserialize – Fix ‘Unable to Unserialize Value’ Error

Running into issues on a site running Magento 2.2.0-rc3.0/PHP 7.0.23

The following issue occurs with all 3rd party extensions either enabled or disabled.

When adding an item to comparison from category or product page or submitting a review from product page we get the following error in the browser:

1 exception(s):
Exception #0 (InvalidArgumentException): Unable to unserialize value.

Exception #0 (InvalidArgumentException): Unable to unserialize value.
#0 /home/___/public_html/app/code/Magento/Theme/Controller/Result/MessagePlugin.php(157): Magento\Framework\Serialize\Serializer\Json->unserialize('[{\\"type\\":\\"su...')
#1 /home/___/public_html/app/code/Magento/Theme/Controller/Result/MessagePlugin.php(135): Magento\Theme\Controller\Result\MessagePlugin->getCookiesMessages()
#2 /home/___/public_html/app/code/Magento/Theme/Controller/Result/MessagePlugin.php(84): Magento\Theme\Controller\Result\MessagePlugin->getMessages()
#3 /home/___/public_html/lib/internal/Magento/Framework/Interception/Interceptor.php(146): Magento\Theme\Controller\Result\MessagePlugin->afterRenderResult(Object(Magento\Framework\View\Result\Page\Interceptor), Object(Magento\Framework\View\Result\Page\Interceptor), Object(Magento\Framework\App\Response\Http\Interceptor))
#4 /home/___/public_html/lib/internal/Magento/Framework/Interception/Interceptor.php(153): Magento\Framework\View\Result\Page\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Response\Http\Interceptor))
#5 /home/___/public_html/generated/code/Magento/Framework/View/Result/Page/Interceptor.php(26): Magento\Framework\View\Result\Page\Interceptor->___callPlugins('renderResult', Array, Array)
#6 /home/___/public_html/lib/internal/Magento/Framework/App/Http.php(139): Magento\Framework\View\Result\Page\Interceptor->renderResult(Object(Magento\Framework\App\Response\Http\Interceptor))
#7 /home/___/public_html/lib/internal/Magento/Framework/App/Bootstrap.php(256): Magento\Framework\App\Http->launch()
#8 /home/___/public_html/index.php(39): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http))
#9 {main}

The error does not go away unless you clear cookies, in particular, the mage-messages cookie.

Any assistance in troubleshooting these errors is appreciated.