My Model Works Then Disappears

I am working out a space flight smulator and when I test my game I can move my model just fine. I have the external camera set with a springarm about 300 units behind my ship so you can see the whole ship. But for some reason almost every time I start flying around my model disappears and the game seems to freeze. Has anyone had this issue and if so, ow can I remedy it? Please help :slight_smile: