I'm getting this error when i'm trying to update the console to the latest firmware 5.5.6U, i already uninstalled Coldboot Haxchi, unplugged my external HDD and restarted the console, still nothing. :
Installing COLD BOOT HAXCHI on Wii U 5.5.0 - 5.5.4 - Sthetix
How to install Haxchi and Autoboot CHBC CFW (Cold Boot Haxchi) - Sthetix