Strange Sort problem - redone

[gtcnetworking]

Hi I have a strange problem that I am struggling to resolve. Hopefully someone can help me.

The site is  VM 4.0.12 10777
Joomla 3.10.11
PHP 7.4.33

The problem seems to stem from how I link searched from the slideshows.
If I link this way

https://www.nsoffice.com.au/index.php/shop-menu/brands/keyword/yankee/view/category/virtuemart_category_id/0/search/true/start/0

And then change the default sort order from name to say price. - it works. I get the same items in price order. Note this link as a search item name - Yankee

If I link this way.

https://www.nsoffice.com.au/index.php/component/virtuemart/
view/category/virtuemart_category_id/564

this is a link to all the items in that category 564.

If you then change the sort order to price it fails !
Because it is now searching for the word "orderby"
My question is why ? There is no "orderby' in the link

And I am not sure when this started
Any help appreciated

ps I cannot update t0 Joomla 4.x yet as I have plugin compatibility issues

Derek