Sidr Firefox sticky nav bug

[dtacci]

Getting a weird bug in Firefox utilizing a sticky nav where, upon the activation of the sidr menu, the icon/toggle that was clicked in the header disappears. It will re-appear after a bit on scroll or window resize, but it's a poor user experience. Does not occur in Chrome or Safari, nor does it seem to occur if I put the button in the main content. Anyone else experiencing this?

Included a few screenshots to get the idea, but always happens in Firefox and seemingly no matter of CSS adjustments will cure it - tried messing with the position values, z-index, displays, opacity, nothing.

In the examples below, the hamburger icon is the button/toggle (I tested with the bare minimum markup, just id+text and it behaved exactly the same), then upon clicked, it disappears, only to pop up again in the right place upon scrolling or resize. Again, does not occur in Chrome or Safari. Any ideas?

[nerdinosa]

I have the exact same Problem. Did you find a solution?

[bagaweb]

Very same problem here as well, have you solved it?