I have a similar issue whith iPhone 8. On one site clickng the three menu bars nothing happened and on the other site the menu opens but nothing happens when clicking submenu items. Both sites are live sites so I had to revert back to and older version (2.0.7) to get the sites running. The problem on both sites occurs with the latest version (3.1.3).
If you need to investigate I will have to install the sites on a staging server for you. Please let me know in such case.
