I have created several menu's and the all work fine accept for this new menu. The only difference with the other menu's is the size. This menu is links to a manual, with about 10 main categories, 100 sub-categories and in total about 2500 links to (standard) articles.
1. Created a new menu
2. published as a mod_mainmeu
settings: menu style: list
start level: 1
end level: 6
always show sub-item: no
1.
SELECT *
FROM jos_components
WHERE parent = 0
2.
SELECT folder AS type, element AS name, params
FROM jos_plugins
WHERE published >= 1
AND access <= 2
ORDER BY ordering
3.
SELECT m.*, c.`option` AS component
FROM jos_menu AS m
LEFT JOIN jos_components AS c
ON m.componentid = c.id
WHERE m.published = 1
ORDER BY m.sublevel, m.parent, m.ordering
4.
SELECT template
FROM jos_templates_menu
WHERE client_id = 0
AND (menuid = 0 OR menuid = 1752)
ORDER BY menuid DESC
LIMIT 0, 1
5.
SELECT a.*, u.name AS author, u.usertype, cc.title AS category, s.title AS section, CASE WHEN CHAR_LENGTH(a.alias) THEN CONCAT_WS(":", a.id, a.alias) ELSE a.id END AS slug, CASE WHEN CHAR_LENGTH(cc.alias) THEN CONCAT_WS(":", cc.id, cc.alias) ELSE cc.id END AS catslug, g.name AS groups, s.published AS sec_pub, cc.published AS cat_pub, s.access AS sec_access, cc.access AS cat_access
FROM jos_content AS a
LEFT JOIN jos_categories AS cc
ON cc.id = a.catid
LEFT JOIN jos_sections AS s
ON s.id = cc.section
AND s.scope = "content"
LEFT JOIN jos_users AS u
ON u.id = a.created_by
LEFT JOIN jos_groups AS g
ON a.access = g.id
WHERE a.id = 1698
6.
SELECT id, title, module, position, content, showtitle, control, params
FROM jos_modules AS m
LEFT JOIN jos_modules_menu AS mm
ON mm.moduleid = m.id
WHERE m.published = 1
AND m.access <= 2
AND m.client_id = 0
AND ( mm.menuid = 1752 OR mm.menuid = 0 )
ORDER BY position, ordering
In the end the solution was simple, but needed two specific steps.
1. First turn on the Cache: Global Settings > System > Cache > ON
2. Go to the module and choose the option "always show subitems" > YES
3. Go to the front end and load a article, make sure you select a child item/article.
4. Go back to the module and select "Always show sub items" > NO