Hi Casey,
Difficult to say from your video, but that "popping back" isn't normal. When the shutter is cocked, you shouldn't be able to turn the winding knob any more.
It can't tell from the video, but are the shutter blinds moving when you are winding the camera, and have you actually got the shutter/mirror to move/fire at any time?.
I would also try the camera with a loaded back, just to check if something behaves differently. There might be something wrong with the interlocks between the camera and back.
I hope you get it working, but you should be prepared for that there might not be a simple fix. These cameras are very old, and very complicated, so it's a bit surprising that they usually work at all after all these years. In this case I would consider returning the camera for a refund, and find another one.
All the best,
Trond