Not sending scroll events to AppIndicators
The panel's Status Tray plugin does not send mouse-wheel scroll events via DBus to AppIndicators. I tried to figure out but could not find the reason. Everything seems to be implemented by
sn_item_scroll() resp., but the DBus method
Scroll is never called which can easily be observed by monitoring the session DBus.
If you need an application for testing that reacts to scroll events, you might try Solaar.