Menu not using proper module chrome

An issue has come up in a site we are developing. The Accordeon menu we are using as a side menu works for the entire site... except for one section of the menu (a root menu item and everything underneath it). On those pages, it displays without any of the module chrome that it should be outputting based on the template. It is a Gantry based template that we created, and should be outputting three extra divs around the module content (the .rt-block, .module-surround, and .module-content divs), but on these specific pages it outputs the module content directly, and as such has no usable styling.

This only happens on the pages mentioned previously, and only to this type of module. Other modules display in the same position just fine, and creating a new Accordeon menu has the same issue (in either sidebar position, as well). Nothing seems different in these menu items, and they are normal Category Blog menu items. There are also no errors in the server error logs.

Any ideas what could cause an issue such as this?

Hi
I have absolutely no idea of what is the issue. The module chrome should be managed by the template, I don't see the relation with the type of module.
check this in the "modules.php" file if your template uses it. Not sure with the gantry framework ...

I think that you should better ask the Gantry devs for this
CEd

After not hearing from anyone at Gantry, we have examined the problem further and found what the issue seems to be caused by, though it is still unusual. It does seem to be something with the module itself. I will update this on the Gantry forum as well just in case.

There were two External URL menu items that had their "Target Window" attributes set to "New Without Navigation". Once these were changed to "New Window With Navigation" the module displayed correctly. This also worked if set to same window, or if the menu items in question were disabled entirely.

The menu items were going to an external site (using https:// protocol, whereas the Joomla site was http:// if that could be important) that isn't live yet, but other than that no real unusual usage of an External URL menu item.

I will also note that the Maximenu CK and the normal Joomla Menu modules in use on the same page have no issues with these "New Without Navigation" URL links.

ok I try to understand, but I have to say that it is a bit difficult
What I don't understand, is

It does seem to be something with the module itself

because the native templating system Module Chrome works like this
this is just an example. You can see that "<div custom2>" which is "extra divs around the module content (the .rt-block, .module-surround, and .module-content divs)" is managed into the template Module Chrome.

module content here >> will only output the module content, then the menu. Here the module can not do anything to remove the wrapper "<div custom2>"

don't understand me wrong, I don't want to say "it is not my fault", but in the joomla! process I don't see how this could be possible that the module is in cause