When I click on the hamburger icon the off canvas menu slides in from the left and the off canvas page slides to the right. So far so good. But when I do the same thing on the sticky menu, the off canvas menu slides in, but the nav does not slide to the right along with the off canvas page and stays on top of the menu. Resulting in unpredictable behaviour...
I think the cause is in the 'left: 25px' on the element, but I can't figure out from where this line in compiled.
See attachements ( 1 original code, 2 with the code line edited in firefox webdeveloper)

Live Url please to analyze the problem!

And the "left:25px" is not the problem. Its a bug, please add this code to your css/custom.css

.uk-sticky-placeholder nav.uk-active {
z-index: 1 !important;
}

Problem solved.