Please see this image:
I don't know what's going on with that icon, but it has been persistent for the past week. It became like that when I forced the shutdown on my Mac because it hanged up. I've just upgraded to El Capitan when it happened.
I've tried the following:
- Relaunch Finder
- Quit Finder and Dock on Activity Terminal
- killall Dock
Nothing worked so far.
As per user24601's suggestion, I've tried the following:
- Turned on magnification. It persists on zoom. Please see image:
- Tried to change position. It still persists: