Sudden Sharing Problems, can't remove user, can't invite user

[mtfm 0]

Hey there,

I'm running evernote premium and was always able to share a notebook with free accounts so far.

1.) I'm normally sharing notebook with another user via the e-mail address. I'm setting the rights to "Can edit and invite"

2.) The other user receives the notebook in the workchat and on click this happens: https://imgur.com/a/yb1gSu3

"It says the user either doesn't have rights or the notebook has been moved or deleted."
But none of the above is true, the notebook hasn't been moved. And the user got rights to edit and invite.

3.) Strangly also when viewing the Sharing Settings of the notebook I suddenly see a user called "Anonymous": https://imgur.com/a/Ax0U8CK

 

Thanks for your help. I don't know what to do. This happens only for some notebooks. Of 10 invitations it happens with 4 maybe.