Active menu item state on all menu items

Have you tried deactivating Bem_Menu_Walker to see if that resolves the problem?

I would suggest removing the plugin and instead either adjusting your CSS or adding class names through menu management. (Each menu item allows you to add a class, if that’s all you need to achieve.) Or, create your own custom walker.

Since these are all anchors, you may need to write some JavaScript that adds an event listener to your menu. When a click/tap event occurs, the JS needs to remove the active class from whatever element it is on and add the active class to the clicked/tapped element.