loading page issues

Hi, I hope you can help with this issue. Iam not full skilled with JS.
Recently I followed the video “Creating a Smooth Sliding Menu” and every seems to work fine until the page is reloaded. The “sliding menu” is always deployed on top first…
If you clicked it works as spected, the “sliding menu” hides, leeting you see the page content. If you want to deploy it once again, click again in the menu button. The problem happens when the page is loaded by first time or reloaded.

Can you share your example? There might be something going on with the initial #flyoutMenu rule where the transform that sets the horizontal position to -100vw isn’t kicking in.