I just faced the issue, that the mobile menu had no items in it.
I fixed it by editing line 1287 in js/avia.js:
var first_level_items = menu.find('> li:not(.menu-item-avia-special)'); //select all first level items that are not special items
var first_level_items = $('#avia-menu').find('> li:not(.menu-item-avia-special)'); //select all first level items that are not special items
var menu was overwritten somewhere I think.
Are you running the latest version of the theme and WordPress? If so then this problem was introduced with the latest version of WordPress, we are working on getting it fixed. Until then please continue using your fix, or install this plugin: https://wordpress.org/plugins/enable-jquery-migrate-helper/, and set the jQuery version to 1.12.4 in the plugin options.
thanks for the reply!
yes both are up-to-date. I will use my fix until I discover more issues i will report back.