The only way Weasel could be caused by cross save is if you're logged into D2 on Steam and someone else logs into D2 on your XBox account on an XBox or the Microsoft Store version of D2. You can't be logged into D2 on more than one account at a time that is connected to your cross save. If your issue is not related to someone logging into your XBox account while you're logged in on Steam then your Weasel error relates to a connection issue and not a cross save issue. And no, Bungie does not provide any service to migrate D2 game progress from one platform account to another. So if you disable cross save then your XBox characters will only be accessible on XBox or the Microsoft Store version of D2. On Steam you will be left with two 1100 characters with about 14 hours of play time on them.

We[i]a[/i]sel's cross save error comes from if you try to sign in to both platforms at the same time. Disabling cross save will not fix it unless someone is actively signing into your D2 xbox while you are playing. [quote] Cross Save: Cross Save does NOT cause WEASEL errors. Players who attempt to log in to multiple platforms simultaneously while Cross Save is enabled on their account will receive a WEASEL error on which ever platform they logged in on first.[/quote]https://help.bungie.net/hc/en-us/articles/360048717852-Error-Code-WEASEL