I can not reproduce your issue. Refer my video below.
Please try this, uninstall IconPackage, reboot immediately after Installation finished. Download latest version available from your account page: https://store.stardock.com/myaccount/products. Install it, reboot again right after the installation done. Once system finished start up. Apply an IconPackage, than try change one Icon and see if you still have the same issue. Report back.
Thank you,
Basj,
Stardock Community Assistant