I'll quote here what I've said on reddit and how I think that it is happening, and how to fix it :

I think I understood this bug as I've been trying to find a workaround for 3 hours yesterday :

I think you've been disconnected in the middle of a animation thus creating the bug. The only thing that worked for me was to connect to the server, do some animation (cutting a bush, pouring water into my canteen, etc...), disconnect and reconnect. That worked for me and my friend. I tried everything besides this one (relaunching the game, relaunching DayZSALauncher, relaunching steam and my computer, verifying game data...) but doing an animation again seems to be working.

That's why I think that when you have this bug, the server disconnected you in a animation state and does not understand why you're not in a animation anymore when you come back. Just updating your animation status should work !

https://www.reddit.com/r/dayz/comments/awysky/visual_glitch_arms_guns_etc/

(From a dev point of view, looks like a boolean isn't updated on server restart ? ... But as I'm not a part of the project, I don't know ...)