I run my own dedicated Valheim servers. I only reboot them once a week and it always saves the world state before shutting down so simple server reboot wont make items lost.
Client has it's own save, your character and it's inventory. Rest is saved in world save that can be on server or your own computer for single player.
I also run ARK servers and only time we lost some items was when we had to revert to older save due a unfortunate fail on updating a mod that totaled our world. So that was a "reset" to previous state of world.
If some one is "resetting" their Valheim world to some previous save state once a day, no idea why the heck.