Hey,

OK I'll try and make the instructions make sense but it should be pretty simple. If anyone has any suggestions on a better way to do this I'm happy to hear them but this works for me at the mo.

The file you need to edit is includes/index_filters/default_filter.php

Line 91 should read if (isset($column_list)) {

Immediately after that line insert the following few lines.

// bof randomise listing after sort by sort order
if ($_GET['sort'] == 'RAND')
{
$seed = ereg_replace("[^0-9]", "", $_SESSION['securityToken']);
$seed = substr($seed, 0, 5);
$seed = (int)$seed;
$listing_sql .= " order by p.products_sort_order desc, rand($seed)";
}
else
{
// eof randomise

Now to activate it do the following

1. Log in to Admin.
2. Configuration>Product Listing>Display Product Listing Sort Order
3. Enter 'RAND' (needs to be capitals).
4. Click 'Update'

You should now have the product listing order randomised for each separate session but the order will not change during a session meaning that you won't have the problem of products appearing more than once or even missing from the listings when navigating through multiple pages.

Hope that helps.