Hi,
1, We dont have this issue and our customer too. Maybe the reason from your config or your module have installed or your hosting config. The log say to magento core code file.
Please refer this links to relsove your issue:
– http://magento.stackexchange.com/questions/43899/troubleshooting-notice-undefined-index-httponly-secure-domain
– http://stackoverflow.com/questions/29046526/magento-frondend-and-backend-show-error
2, Your site slow maybe the reason from:
– You have anable log
– You have disable cache
Have a nice weekend!
