In my experience this is hands desync. It's usually the same reason why bullets aren't doing damage, either. Relog "fixes" it.

I've been experiencing this constantly in Exp 1.06. I had to relog several times in the first hour of playing. Unfortunately despite happening frequently I can't find a consistent repro. It did seem to happen most-often while handling the double-barrel and the new Blaze.

Edit: Played some more Exp tonight and this is simply not playable at the moment. I know the holidays are fast approaching but this really needs to be addressed before Stable release.

It happened to me as well. I think it reproduces when you can't pick an item (seemingly bugged) from the ground, but I died too thanks to not registering bullets and z hitting me harder than my life. @Geez please do something. Thanks.

i have the Same Problem
but it happens when you have an item in you Hands and there is no place in inventory
so after like 5-30 min having that item in hand zombies can attack you but you can't and if you drop the item from your hands you cant pick it and need to relog and after relog item is disappeared xD
1.06 EXP