ฟอรั่มสนับสนุนของ Firefox

I have included a website on the list of exceptions for deleting cookies when Firefox is closed. When I go to the website the icons on Firefox for it show "enhanced tracking protection off" and "You have granted this website additional permissions". This website uses cookies to recognize my computer and not to require a one time password. However, when I close Firefox despite the fact that the website is on the exception list, cookies are deleted and I have to keep re-entering the one time password. I did turn of the checkbox for deleting cookies when Firefox is closed and now I am no longer asked to enter the OTP after Firefox is closed.

I assume this is a bug. Does anyone else experience similar issues? Is anything I can do about it and be able to use the exception list as intended?

Thanks.