When a pack is opened all icons are loaded for the items in the order of how they are listed in the categories, so there is a noticeable delay on all actions until all icons are loaded. The more packs you enable for a base, the longer loading will take.
Are the purple parts unresponsive in fullscreen too, or only in borderless? Since the screen aspects are different in all 3 cases it’s an important detail so I could reproduce the issue on my end.