Customized view icons in mail NTF, changed to default when upgraded to new version

Hello! We have a customized mail template and we have a customized view in it, but we’re trying to upgrade the design of our template the icons used to all of the views were changed to the default icons after the upgrade. We ensured that the ‘prohibit design and refresh/replaced’ is ticked before we did the upgrade but still changed the view icons. Though the formula views are still intact. Any idea what were doing wrong here? we’re upgrading from 6.5.2 to 6.5.3. Anybody who can shed light on this problem?