It happens on everything in our map thats a SG entity, even after restarting UEFN. In video I am also pressing Undo and it doesnt come back either (and unhide ofc)
What components are you using more specifically? Anything special with your entity setup?
If you create a brand new project and just use that same mesh, does it work? Do basic shapes work in an empty project and in your project too?
This will help us isolate if this is mesh/entity/project specific!
Yes, it happens on a new project as well (I tested with an empty prefab with a mesh component). Is your hotkey for H set to Toggle Selected Hierarchy Visibility (in editor preferences)?