After project deletion, project tab is not accessible without logout & login

The expected behavior for deleting a project will be:

• go to the project settings page

• click delete button and confirm it in the popup

• delete is done and you should be redirected to the projects list page or homepage

After that, if you try to access the old project url, it will show you that Record not found error. If what you were saying is the deleted project still appears in the projects list page, that's probably a cached view. Hit f5 or do a hard refresh may help.

Although I purposely enter "https://translate.openstack.org/" URL and click "Project" tab, the error message is shown - it does not work
I agree with your opinion: that's probably some cache data containing the old project information in local web browser side. Unfortunately, from my trials, "F5" refresh button did not solve the problem.

It might be a so low priority
But it would be a bug for Zanata project management admin users.

This is indeed a bug. It's not browser cache but our internal cache. It tries to reuse the project you just accessed which is deleted. The workaround is either log out and in, or go to another project (either you can search or via dashboard page) then project list page will be accessible again.
Please note the projects list page no longer exists in version 4.x. Considering deleting a project is a rare operation and there is workaround, I am not sure if we would fix this bug in 3.9.6. I will test it in our current release and make sure it's not there.

Confirmed 4.1.1 and master do not have this bug.

Closing this per Patrick's comment as it's no longer a problem in the most recent version.