I dont understand how you have a menu of menutype either main or menu as Joomla doesnt let you create a menu with a menutype of main or mennu

Please change the Menu type. The terms 'menu' and 'main' are reserved for Backend usage.

@brianteeman The problem occurs when menu with menutype menu or main is created in Joomla! version which did not prohibit it.

Today I debugged a site that started seeing frontend menu items in the components menu in the admin! This only happened on update to Joomla 3.7.0

On investigating #__menu those menu items were of menutype "main" ...

Therefore Im guessing, that in some earlier version of Joomla we allowed it... and in 3.7.0 something 'changed'

@PhilETaylor see #13619 this is the cheange.

Im guessing, that in some earlier version of Joomla we allowed it... and in 3.7.0 something 'changed'

Truth is exactly the opposite.

Knowing this fact, this issue should not be caused by said change. I/we need to investigate deeper.

@izharaazmi Menu disappear only on legacy web sites see @PhilETaylor. I also diagnose this problem for someone one of Polish group about Joomla! on Facebook. Result: menutype = menu and we have the problem described above.

I can confirm the menu on frontend disappears.

@mydutchtouch Do you remember on what version of Joomla! site was installed?

I upgraded today from 3.6.5 to 3.7.

I will ask otherwise. When more or less this website was created?

Website was created 3 months ago using a template. Not sure how old the template is.

@izharaazmi Any idea how to detect which elements should be in the backend menu? In the current situation where we can not trust menutype for updated websites. The simplest solution is a #13619 rever and adding a problem description and manual solution to the 3.7.0 Release FAQ.

Can you please explain more as how to reproduce your issue here so that I
can come up with the real culprit and solution. As of now I am unable to
reproduce and hence can't fix anything. Thanks.

1. Install Joomla! 3.6.5 with sample data
2. Change the menutype of any frontend menu link in #__menu to menu or main..
3. Make backup of the website database.
4. Make updates to 3.7.0 with com_joomlaupdate.
5. Result link from 2 in components admin menu.

@izharaazmi I updated the description in the previous comment to be 100% understandable. Sorry for the previous version. I was really in a hurry.

you cannot create a menutype with (main, menu) in 3.6.5

so i guess we should replace this from #13619

UPDATE `#__menu` SET `menutype` = 'main', `client_id` = 1  WHERE `menutype` = 'main' OR `menutype` = 'menu';

to this one

UPDATE `#__menu` , `#__menu_types` 
SET `#__menu`.`menutype` = 'menu_main_is_reserved'
    ,`#__menu_types`.`menutype` = 'menu_main_is_reserved'
WHERE `#__menu`.`menutype` = 'main' 
AND `#__menu`.`menutype` = `#__menu_types`.`menutype`;

cause the only the term main is reserved now

@alikon Yes we cent create main or menu in 3.6.5 but earlier it was possible. Can you create a PR with your changes?

Set to "closed" on behalf of @franz-wohlkoenig by The JTracker Application at issues.joomla.org/joomla-cms/15671

closed as having PR #15695

New PR is #16577 . Please test as soon as I have updated the testing instructions there.
Btw. does anybody know which Joomla version can be used to create a menu type "main" or "menu" for the site (frontend)? Does that work on a 3.6.5? Would be good to know for easy testing instructions.

PR #16577 is ready. Please test.

@wojsmol Please test #16577 (issue tracker link see here).