First that makes no sense, why would only once fence appear and not all if I accidentally toggle it.
Only my bottom fence appears at random when launching a full screen app. This fence is a folder portal fence. The others don't come peering through like that.
Second I don't have that option in my Fences.
I think there is a rendering problem with Fences 4, HDR, and Win 11. When I screen capture it looks ok, like the above image, however when I am looking at it at the screen the menu text font looks broken. I was able to capture this with with OBS and took a screen cap of that, see the below capture and the menu text.
I am using HDR in desktop mode, when I turn off HDR this issue disappears and the menu text renders correctly. I think the fence peering through the full screen application is related to this problem. Again non issue on Fences 2 on my other Win 11 machine, on Fences 4.