Help making fixed slide out menu scrollable


So I’m having issues making the slide-out left menu I am using for my site scroll. I have set the VH to 100 and set overflow to scroll however when viewing this in a browser window that is smaller in height than the content of the expanded slide-out menu it gets cut off with no way for the user to scroll on it.

Here’s the live link:

To replicate the issue, click the right hamburger icon on the main navigation menu and try to scroll the slide-out menu.

Anyone able to help?

Here is my site Read-Only:

Any updates on this, kinda stuck…