If you find this cryptic:

) map each K2 category into a separate menu item (this is what I do).

I am not sure what else to say.

I am not sure what else to say.

K2 doesn't support nested category SEF URLs

There is no point in continuing this discussion I am afraid.

My k2 urls are in a bit of the mess now.

To respond to some of Krikor's questions (as you can see from the credentials I sent through the contact form):

You need to either map all categories into menu items OR use K2's advanced SEF.

Using both can result to not-so nice URLs.

I have mapped all categories into menu items and I am currently having K2 advanced SEF OFF

Furthermore sh404sef's cache seems to have issues when it comes to purging.

I have been purging urls using sh404sef. I am wondering what issue you have experienced?

Finally when using Advanced SEF if you select "Use the item's category" in the Prefix for item URLs setting then you will get an extra prefix,

As indicated above, my k2 advanced SEF is currently OFF, it therefore should not have effect on the menu mapping of Joomla. The urls I am getting are:

category/menu-item/id_subcategory/k2 article.html
(the menu-item here is the menu item for the k2 sub-category)

I would appreciate any advice as what I causing this?

Best regards

En Jie

I have mapped all categories into menu items and I am currently having K2 advanced SEF OFF

They are disabled because you sent me credentials and I disabled them myself.

The default URLs are /menu-item/item/id-itemalias.
Since you were getting completely different URLs, to be more precise,
category-prefix, no ID in the URL and no /item/ this is the result of K2's advanced SEF.

Without K2's advanced SEF you would not be getting these URL patterns.

Finally in your site the URLs are:

staging.domain.com/blog/hot-topics/item/71-the-recent-surge-of-pu-erh-tea-prices-in-china.html

or
staging.domain.com/blog/green-tea/item/167-green-teas-are-not-all-equal.html

which are of the pattern:
/main-category/subcategory/item/id-item-alias.

You can reenable K2's advanced SEF in order to remove the /item/ prefix, just don't use the item's category as a prefix.