I always disliked systray scrolling (and worse where the icons just trade places [blocky scrolling]). Anyhow those OnLButtonDown events should fire only once (try having them !alert instead). If you should like them to repeatedly fire, try starting a looping timer OnButtonDown and killing it OnButtonUp using the module timer-0.5 .

You have VTraySettingsCompatibility set to be true, so you should use !SystrayScrollIcons instead of !VTrayScrollIcons, I think (see !about for a list of available bangs).
And IIRC, the argument to that bang may have to be quoted (try the other if one fails to work).

Little things :)