Thats a script deal, not core and relates to the distro so I've moved it.
The gumps for it are pre-rendered on POL start and stored as gumps ready to be sent (for speed). The script that does this is in the control package's initializer directory and the script is cmdbarmenus.src
You could also change the gump it wants to use in the gumpinfo.cfg file in the gumps package.
Looking at your screen shot it looks like you have custom gumps on your shard. You probably need to go to gumpinfo.cfg and renumber them to match the gump ID numbers in your shard's files.
On POL restart I do believe it completely rebuilds the cmd bar gumps so that should be enough, and under settings, if youre an admin you get a button to rebuild the gumps there as well.