When our projects were upgraded to Architect 2.1, the preventHeader attribute was erased from the ext components across all of our files. Every location that had a preventHeader requires you to go to the component, search for header, enable header, then disable header to get the same functionality.

This means that a manual process has to happen where exports pre 2.1 upgrade are gone through to look for every instance of preventHeader, then setting "header" to false in that component by hand.