Demobrowser freezes weston

On Archlinux and weston (without xwayland), launching demobrowser with gtk3 theme or the default theme (QT_QPA_PLATFORMTHEME=) results in eventual weston freeze - e.g when clicking a menu item or on tooltip or popup. Only SysRq keys can then be used to exit the compositor.

The same issue does not occur on quicktestbrowser if launched with QT_QPA_PLATFORMTHEME=gtk3 but does occur if launched with default theme QT_QPA_PLATFORMTHEME=.