At the train station north and east of Gvozdno there is a van parked near the edge of the parking lot. I opened the trunk and crawled (prone) inside. Then I clicked my scroll wheel and the van's trunk shut. When this happened I slide backwards through the van door and through the fence behind it (completely involuntary- I had no control over this movement). I was laying prone suspended in the air. Going to crouch caused me to no longer hover and I dropped to my death.