Throwing me out of mission 12

I’m having a nightmare with being thrown out of the game to the home screen when im trying to load up in solo campaign. I’m up to battle of sunaion but every time I try to load my saved game, it tells me I’m deploying, counts down from 5 to 1 and then I see a timer in the bottom left of the screen before it throws me out of the game completely. I’ve contacted xbox who don’t think it’s a problem with the console, I’ve removed and reinstalled the game, cleaned the disc etc. Help!