[Solved] Problem with multiplayer: "this character belongs to another player"

[Asdfk]

Hi there, I'm having an issue playing multiplayer with a friend.

So we have been playing the new update 1.6 from scratch in a new savefile through steam.
We reached Winter just yesterday but today that ("this character belongs to another player") problem started to appear, making It impossible for this friend to join the farm.
We don't know what is causing this but I tried a few things and all my hopes were put on savefile editting, but I only get the game to crash when trying to run that savefile.
However, I discovered one thing with savefile editting and that is that for some reason the userID that is taking from my friend is 0 instead of the usual long ID number that It should be. We checked this by making room at the farm by buying a cabin so he could join and saving after one in-game day, then looking at the savefile userIDs.

Does anyone have any idea what is causing this problem? I've seen in other websites that savefile editting on this new version can cause problems and we can't rely on It.

Thanks in advance!

[Asdfk]

Solved: We don't know why or what was causing this but an old uninstall and reinstall trick solved It.