Lack of drive space is a different problem, although admittedly sometimes the symptoms can be similar.
Running Windows and/or the game on a drive that lacks sufficient space for both of them to maneuver properly will lead to stability issues on the part of the game and just about anything else Windows has to run. Even web browsers will malfunction under such conditions. We generally recommend at least 15% free space for Windows and at least 35 GB free, whichever is higher.
Error12s are more typically RAM and graphics memory related and pertain to the current game session being played, not drive space, but again when operating with not enough space to work with just about anything strange can happen.