I'm experiencing this error on my site quite often:
Exception #0 (Magento\Framework\Exception\NoSuchEntityException): No such entity with cartId =
It's not using multiple stores, so the entity_ids are not an issue as stated in many other solutions I have tried.
I can't find anything helpful anywhere else.
In my case it was an email sending issue. The email config was trying to send from ABC@domain as XYZ@domain.
I changed to send from ABC@domain with a BCC XYC@domain and all is well again
In my case the Firefox plugin uMatrix was causing the issue.
I described it here:
I had the same issue using paypal. Magento 2.2.8 iways paypal plus module multisite setup
Every time I confirmed the checkout on the paypal site I ended up in the cart with the message "no such entity with cart id =".
It turned out that uMatrix is the trouble maker in my case. Even when disabling it for my particular site it caused the error. Only after completely disabling it in the addons the error went away.
