I have this same issue.. its in a vauxhall/opel/GM depending where your reading this. Originally it would flicker off for a second and lose all settings so was an issue with permanent live.. i needed to change the permanent and switched live over (Vauxhall idiosyncrasies) after doing this the same fault would happen but would not lose settings, so perm live is now steady.. i then added a tap wire to from perm to the switched live feed in order to give a steady 12v supply. As soon as i make the connection, cabin fans start up and stop upon disconnect.. same happens with the head unit so all working as planned.. however whilst driving the radio still loses switches live even though it has a permanent live tap running to it… really driving me mad now. Think the only option left is to get a new head unit and see if that cures it