For me, nothing is wrong at the beginning of a new session, but the bug appears after I have achieved a drag and drop action (in nautilus or firefox) and stays until I restart the session.
If I don't do any drag and drop action, the launcher doesn't seem to show over fullscreen apps.
I also can confirm that enabling workspaces fixes the issue on my computer (laptop with an external monitor).
For me, nothing is wrong at the beginning of a new session, but the bug appears after I have achieved a drag and drop action (in nautilus or firefox) and stays until I restart the session.
If I don't do any drag and drop action, the launcher doesn't seem to show over fullscreen apps.
I also can confirm that enabling workspaces fixes the issue on my computer (laptop with an external monitor).