I'm new to speedrunning. I used the Livesplitter on Very Easy Difficulty for the PC version of MGS 3 HD edition. It worked fine. I then tried on Normal Difficulty. But it keeps stopping right before The Boss fight. What could it be?

Edit. When Livesplit stops (before The Boss fight) that time is shown as the Credits Time. I tried another run and this time it stopped in the middle of the mission with Eva, before The Boss fight (as opposed to the end of that mission).

I had done one run as NG (I assume that's when you start a new game and don't load it from a previously finished run) and my time was recorded. Then, I did a NG+ and the Livesplit stopped right before the credits--It was the part right when I grabbed the revolver for the dual vs Ocelet on the plane.

Edit. I'm playing the PC version of the game.

Edit 2. After having a little bit of time to sleep on this and review the rules that are on this site, my educated guess is that I probably used some camo before the fight vs The Boss which is not allowed and that is what stopped the clock.