Where are you in the game?
If you start a new game, can you reproduce this? Moving a bit from the initial character position can trigger an auto save, which might overwrite one from your current playthrough. If you don't already have an honour mode difficulty save, starting one would avoid that problem, since it uses a separate, single save slot (in the difficulty list, after selecting Tactician there is a choice between Regular and Honour).
Does the game crash if you start the game from a different user account, if available, and start a new game? A different account would give a separate drive space for saves.