Thanks for getting back to me.
I tried disabling all plugins and custom css and it still happens. I also tried creating new empty site, new install of Pro and new basic header with just a ‘single navigation’ collapsed element to test, and the issue also arises.
I found a thread from a user with a similar (though not identical) issue here: https://theme.co/apex/forum/t/navigation-collapsed-nested-sub-links-broken/3084
The recommended fix (below) from that thread worked for me, though with the same side effect that user reported — it breaks transitions.
[data-x-collapse=“opening”]>ul.sub-menu {
overflow: auto !important;
height: auto !important;
}
The staff member in that thread mentioned it being a known issue, so hopefully it’s fixed soon. Thanks.