Easy way as above described:

1. Get your self killed. (jump from a building or let a friend kill you)
2. Disconnect from the server (since you won't die instantly, after a reconnect you are dead)
3. Never get your stuff back. Play happily after.

Or the long way if you are not ready to lose all your stuff:

1. Join a server, drop an item.
2. Join another server, see if its fixed.
3. If not fixed, repeat steps 1-2

While dropping items doesn't appear to work, the item IS indeed gone if you connect to an other server, same goes for picking items up again.

To accelerate the whole thing you can drop a bunch of stuff like most of your food or most of your ammo and then connect another server.

Yep. Not outdated server. I could fix it by getting myself killed. Here is how:

1. Connect to any server.
2. Find a way to die (jump from a building/light house or let a friend shoot you)
3. DON'T GET YOUR STUFF BACK.

The issue has something to do with your gear. My friends had no problems until i joined the server, then they started to have the same issues as me. I also got my self killed once, had it fixed, then went to pick up my gear again and had the same problem again. So I think something in the gear breaks and can't sync with the server. Just get killed and never look back, I am roaming happily since.

Yeah i know. I had exactly the same stuff + i couldn't even take my gun in the hand. It fixed it for me by dying and starting over. Did you even try it? Testwise you can enable the experimental build, which has its own character (no worries, you won't lose your normal one if you start a experimental one). If you can interact with your inv (i.e. put the batteries in your flashlight) then a fresh start should fix it for you, too.

And I am not saying that dying itself fixes the issue, but rather getting rid of the gear that is causing the issue, so you can play again.

Same issue here from Germany. Can't even take my gun in my hands. Can't interact with anything. Stuff i tried to do, like putting something on the ground, only is executed after i rejoin the game. Then i see the item lying there, but can't interact with that one either. Know a few people more that have this.