Clear the cache of your Xbox as instructed below. This will not erase any of your games, data or saves.
1. Power down your Xbox using the Xbox controller or the Power Off button on your Xbox
2. Unplug the power cable from the back of your Xbox
3. Wait at least two minutes
4. Plug the cable back into your Xbox
5. Turn your Xbox back on
Once done, try loading an earlier save file created before encountering the issue and progress from there.