In CET 10.5 and older versions, we used to call rebuildAllToolboxCards()
when the main app window got resize and resizeEnd. These calls (of course) produce a lot of slow response and flickering, so they have been removed. This means that your custom toolbox cards will no longer get rebuilt on app window resize, and there is no reason they should have to. However, if you really need this, please contact developer support!