I had the same problem. Also sub-menus were not showing properly in small widths (mobile i.e.). I think it’s some kind of bug, so I strongly recommend to downgrade to v.1.4.1 to make it work again.
I think you can get it from here.
Before any plugin or theme update you should always make a complete backup of your site. If you did it, you can simply take the theme folder “quest” from your backup and replace it in wp-content/themes.
Hope it helps.