There are many exceptions happened with the following stack trace:
Error during unserialization
Can I understand what is the error about and how to fix?
I am using Magento CE 220.127.116.11 with PHP 5.6 hosting on Windows IIS.
Seems like this is known bug and it is already fixed in SUPEE-8788 patch.
To resolve the issue , kindly install this patch in your magento version and that will solve the error.
Here is the reference link for how to install/apply patch on the existing magento application - https://devdocs.magento.com/guides/m1x/other/ht_install-patches.html
The Magento version is CE 18.104.22.168
It should already have the SUPEE-8788 applied in the version itself.
So I guess it should be a different issue?