Here is a video of a kill on top of veresnik hill, the body is accessible for a short while before beginning a physics stage lasting a few seconds. after which the body becomes inaccessible.

http://www.twitch.tv/sacriel/v/34959132?t=7m20s

It is my belief that after a kill, the server and the player's client both perform local physics simulation on the body, if the body on the server-side simulation slides away (currently the DayZ physics model does not include traction or drag, so bodies slide on angled planes as if they were glass) then the server removes the clients ability to loot the body. I draw an example of my hyptothesis here.

If a kill is on a totally flat plane, there is no chance of the two physics simulations being far enough apart to cause problems, but on an angled plane it is fairly common for the body to slide away on one client and not the other. This is also demonstrated on stream when my squad kills somebody, each of my squadmates will see a totally different local version of the body, only one person will be able to loot the body - the one who lucked out and their personal physics simulation ended up approximately matching the server's simulation.

This is my hypothesis and proposal of a potential fix http://www.twitch.tv/sacriel/v/34959132?t=9m40s

another fix may be to loosen up the range in which you can loot a body. Maybe extend it to 2 meters instead of point-blank - this would allow people to loot bodies which have 'only' slid upto 2 meteres away from the server-side simulation. However this may have undesired effects such as allowing people to loot bodies from an unrealistic distance.