The problem is that the old way that Qt had to tell Gtk not to use the overlay scrollbars (ubuntu_gtk_set_use_overlay_scrollbar) is now basically a noop since the new overlay-scrollbar hijacks the scrollbars at a different level (does not use os_scrollbar_new as it used to use).
It works for most Qt based programs because the new overlay-scrollbar code includes a check to not load itself if the qt_startup_hook symbol is present in the main binary of the problem, thus the issue only happens in programs like "vlc" or "bzr qlog" where Qt is loaded in a plugin of the main binary.
The problem is that the old way that Qt had to tell Gtk not to use the overlay scrollbars (ubuntu_ gtk_set_ use_overlay_ scrollbar) is now basically a noop since the new overlay-scrollbar hijacks the scrollbars at a different level (does not use os_scrollbar_new as it used to use).
It works for most Qt based programs because the new overlay-scrollbar code includes a check to not load itself if the qt_startup_hook symbol is present in the main binary of the problem, thus the issue only happens in programs like "vlc" or "bzr qlog" where Qt is loaded in a plugin of the main binary.