Please disable third-party plugins and customizations (if there are any) and check if this issue persists. If you use a caching plugin, make sure that caching is disabled for logged-in users.
Also, Please refresh the permalink structure in Settings/Permalinks (choose any structure with %postname% if the default one is selected) and check if this issue persists.
If have done as you suggested and the problem still exists. I have decided to move to a Linux/Wordpress deployment and this works fine out of the box. I expect some compatibility issues using with IIS.