Mobile view: Site menu & messages respond only after all the page contents loaded?

I was playing around with Elgg 1.12.3 and Aalborg Theme. I have a heavy frontpage (with Twitter widget and many other stuff to display) which uses Widget Manager's custom index. Logins are directed to this frontpage.

I have noticed the following issue on the mobile phone view:  The frontpage is displayed but when you press the site menu symbol (so called "hamburger menu"), it does not respond. The same with any messages displayed. When you click on them they do not disappear.

Eventually the site menu symbol (and the displayed messages) starts to respond and I think it happens only after all the details of the page is loaded. I think it is the same with the message.

I am not sure if it is core, Aalborg Theme, or something else. I am not sure but in the default theme, the site menu seems to work right away.

My workaround is redirecting the control away from the frontpage to a page with lighter content.

Has anybody experienced this? Any ideas why it might be happening? or make it respond?