Sorry for the lengthy report but this is a series of related events and a serious issue if it's reproducable.

I joined a server to meet 3 friends at Balota Airstrip. While sprinting down there from up north, one of my friend's game crashed to desktop for no apparent reason (I forgot to ask if he has seen any error message, sorry).

After he logged back in, he was standing right next to his own character, that wasn't removed from the server after the crash. My friend (the clone) shot the original character, and looted the body. The other 2 guys confirmed this.

When I finally arrived there 20 minutes later, I saw only those 2 other guys roaming around the strip. The clone was completely invisible, only to me though. The other guys could see him.

I had a bipod for him so I dropped it on the ground. He said he took it and attached it to his weapon, but for me it was still lying on the ground. So I took it back into my inventory and attached it to my gun. We thought it was a duplication bug.

Later that night, we switched servers. Then my friend was finally visible to me. But the bipod was gone from his inventory. I dropped it again and this time it didn't stay on the ground after he took it. He didn't lose any of the items he got from his dead character though.