Ok, so the error is related to the reference itself. This Members Collection that you have, it is not the same one that WIX Users API is using for login. You can check the ids to see the difference. Usually the WIX Users API gets the user from the PrivateMembers Collection, if I’m not mistaken.
Try console.log(wixUsers.currentUser.id) and compare the returned id with the one in the Members collection.