Geez - This may be related or separate. I've had zombies popping into/out of ground. https://youtu.be/5LUcPnAersc?t=26s

I can confirm Zwan's report. I can upload another video. Additionally, logging in/out and swimming will also not fix this issue. The barrel cannot be thrown (dunno if in Zwan's, only scanned it)

In my case, bug was triggered when I picked up the barrel and my friend opened the lid at the same time. Layman's guess... Barrel is added to hands then it's state changes to the open version.

Maybe getting into/out of vehicles...? It force empties your hand and drops whatever you had if you don't have a place to put it. Didn't have a chance to try that.

Edit: They on it!