Well, there’s your other problem. Never, ever, ever store your video media on your boot drive. The drive has to do way too much work when it has to run the OS, run the NLE, and read, process, and render the video all at the same time. There comes a point where the drive just decides it’s too much and the app goes down.All on my C drive.
Get an external drive on the fastest bus you have (ideally USB3 or Thunderbolt). Make sure the drive spins at 7200rpm. Use that for all of your video media, render files, etc.