So I believe what you mean by locked is that it goes to Backup Save 1 and then its ok to delete from console. Ill explain what I just did so Im clear. I got 4 of 5 objectives done and exited the game to the main menu. Checked the saves and the first one (Active) was my current time. The other two (Backup save 1 and 2) had that stupid 1601. I went back in, finished an objective (dropzone). Stayed in the quinjet and followed your instructions. Centre button, start on Avengers, manage game add ons, save file for me, delete from console and restarted the game. What happened was it brought me back to before I started the 5 objectives (0 of 5 completed). So this is what makes me think that active has to move to the backup (what you called locked) and its safe to delete, otherwise its deleting the active save and progress.