Multisite shared content fields have data missing

I can confirm that this looks like a problem in D6 with CCK and shared tables:

I have a two CCK types - source and story. In a multisite setup, I share tables using the normal Drupal db/table sharing mechanism for a pretty standard set-up shared content installation with a default site and another site, site1

Below is part of settings.php for site1, which shares content with the default site:

[..snip]

$shared_prefix = 'default_site.share_';
$db_prefix = array(
'default' => 'site1_', //differ for each subsite

'sequences' => $shared_prefix, // shared content
'node' => $shared_prefix, // shared content
'node_revisions' => $shared_prefix, // shared content
'node_type' => $shared_prefix, // shared content

[..snip..]

//CCK content types
'content_type_source' => $shared_prefix,
'content_type_story' => $shared_prefix,

//CCK content fields and groups
'content_group' => $shared_prefix,
'content_group_fields' => $shared_prefix,
'content_field_source' => $shared_prefix,
'content_node_field' => $shared_prefix,
'content_node_field_instance' => $shared_prefix,

[snip...]

In my default site - which owns the default_site database - all the content types are fine. They were established in this site. But in site1 none of the fields I've added to the content type have data filled in when they are displayed. Editing a story originating on the default site in site1 shows the correct fields, but no data for the fields.

After a lot of debugging, I tracked the problem down to the content_cache table. IMO it should be possible for each subsite to hold it's own cache, but this doesn't work for cck fields: to see the info I have to share the default site cache_content table.

The cache_content table does not appear to be properly rebuilt in a shared set up. Or that's my current guess as to why it's got different data in it after a cache clear and redisplay of the content.