After updates on 7/26/19 the wifi applet has a black box around it and the icon is distorted regardless of theme or icon set. How would one troubleshoot this?
Known issue upstream. Restart the panel or logout and login.
Personally I use the network applet from budgie applets rather than this old network manager system tray app.
I removed the system tray applet and added the network applet. Work around complete! Restarting the panel removes the black box, but doesn’t help the icon appearance .