Mobile site sometimes displays Double stacked header with duplicate logo text

Hello WordPress world!

I’m somewhat of a WordPress newb, but I know enough to know that the problem I am having is absolutely bizarre. When viewing our site on an iPhone (haven’t tested other mobile platforms yet) there is an intermittent issue where the header of the site is duplicated and stacked on top of each other. The normal logo text will be displayed with the correct font (Allura). But on top of it there is an extra header logo text displaying in the Lato font, which is the font we chose for our headers. The mobile navbar button also displays incorrectly. Instead of showing as the small triple line square button, it displays as an elongated button with the word ‘navigation’ fully spelled out, which looks terrible!
It seems like the problem mostly occurs shortly after making any sort of changes to the site.

Here’s the link to our site:
islandpartydj.com

The link below will take you to a picture I made with a side by side comparison of the mobile site. The left side shows the mobile site as it should look, and on the right side you can see what it looks like when the problem occurs.

https://i213.photobucket.com/albums/cc48/SpiffyNaJiffy/Mobile%20Uploads/image_1.jpeg