Swiping gestures in iOS 11 Safari are problematic for C3. Swiping from the edge sometimes switches to another tabbed website page instead of opening a panel. And when a panel is open, like the color palette of the animation editor, swiping from the edge changes the current panel’s settings instead of switching to a different panel.
This is why we have a prompt recommending to add to home screen on iOS. When you run from the home screen, it lets you use the side-swipe gestures without trying to do Safari's back/forward navigation.