I see the demo link and get a blank page and can´t understand why. This is the case on most pages except Kitchenlabs - Marcas and still the navbar will only appear for a few seconds and everything turns white.
When was the last time you published the theme? Did it happen after a specific update that you remember applying?
The only thing I can think of is that I have noticed issues when removing elements that are used within a page load trigger interaction but you’re not using that type of trigger. In your case, the elements fade-in when they’re scrolled into view using the native Fade animation: