CB

Was able to replicate on this test site:

tpl.cbdemosites.com

I was able to replicate the following:

Clean Joomla 3.4.3 site with default content and default (protostar) template.

If I view on my iphone 5 (simulator does not seem to simulate properly this use case) I am able to single click on the small menu icon (3 dashes) and it expands just fine.

If I install CB on the site, then the menu does not single click expand.

If I unpublish the CB Login module and the CB Online module then single click expansion works again.

Based on this I can only conclude that there is something in CB code that is breaking this for all templates.

Could not confirm on my android phone using mobile built in browser and mobile chrome. Both working perfectly fine. cbTabs jQuery is the only CB jQuery loading on the home page where you've confirmed the issue and I see nothing in it that can cause this.

That dropdown usage is jQuery powered by Bootstrap. This could be an issue of jQuery conflict (missing namespacing in Joomla bootstrap usage). The only jQuery in cbTabs that could possibly be a culprit, but incredibly unlikely, is the below.

$( document ).on( 'click', '.cbTabNavExternal', function( e ) {

However as it specifically targets the class cbTabNavExternal I don't see how it could possible conflict.