Page Not Found redirect not working for some of my deleted products

[all4coffee]

I have a different sort of problem - all mistyped URL searches to my site show the page_not_found as they are supposed to and nicely returning 404 Not Found headers. Also products which have been removed from the catalog and redirected via .htaccess return either the 410 or 301 headers as needed.

The problem I couldn't find solution for is with the pages for products which have been removed from catalog but I don't want to redirect them with 301 or 410 if this can be helped. I imagine that since the deleted products don't exist anymore, typing their former URL would generate standard 404 Not Found header and display the page_not found without the need of redirecting them one by one.

Example 1 - accidental URL typed/mistyped returns 404 response:
http://www.all4coffee.com/xxxx

Example 2 - redirected in .htaccess, old directory returns 410:
http://www.all4coffee.com/gifts

BUT

Example 3 - removed product URL and not redirected in .htaccess (other than the line: ErrorDocument 404 /index.php?main_page=page_not_found) hangs in Browser and displays "Cannot display in Browser" message. Server header check shows however 200 OK. I checked database and confirmed that the product is not there anymore:
http://www.all4coffee.com/monin-banana-p-109.html

I don't understand why. Logically since the URL for the deleted product doesn't exist, the result should be 404 Not Found. Where am I wrong? I'm using ZenCart 1.37 and would appreciate your help. Thanks.