In the horizontal- and vertical-navigation is a configuration property 'openAll'.
This value should achieve, that all sub pages get rendered in the navigation, not only the active one.
So a JS could fetch all sub pages and provide these drop down menus.

The property is ignored, because the according bean 'info.magnolia.module.templatingkit.templates.Navigation.java' is not populated:
The variable for the property is named different:
private Boolean allOpen;
and its setters and getters.
So the setter is never called and populated -> always false.

I tried to fid out when this error came in, but in all previous bootstrap files of the site config it was always openAll.
In all previous versions of the bean it was always allOpen -> looks like it never worked, what surprises me. I thought I've seen it working.

Workaround:
rename the property in the site configuration to according to the bean: allOpen