People picker configured as cross-site lookup. Gets the following error “Invalid data has been used to update the list item. The field you are trying to update may be read only” when the filed has “Person or Group”
Title
People picker Lookup “Invalid data has been used to update the list item. The field you are tryinDescription
Cause
To use cross-site lookup you should have Single Line of Text field. That's why you received an error in the field that ad Person or Group type.
Resolution
Cross-site lookup is the capability of the List Form to refer to multiple lists in different sites.
To use this feature, create a single-line-of-text field, not a lookup field. Internally, the List Form will store the field value in this format: siteUrl;#listName;#listItemId.
Here is an example of when to use the cross-site lookup field. Let's say that you add a DocumentType field to the metadata of every document that you store in the document library. One way of doing this is to make this field a choice field. However, if you need to change the options for the DocumentType, you have to go to every document library in every site to change it. The same problem occurs if you make the DocumentType field a SharePoint lookup field (because SharePoint can look up a list in the same site). The solution is to make the DocumentType field a cross-site lookup field. You can create a DocumentType list in a centralized place and create a DocumentType field (as single line of text field) in every document library. Configure this field as:
<Field Name="DocumentType" DisplayFieldName="Type" SortField="Type" AutoPostBack="true">
<List SiteUrl="../../.." SiteName="Dashboard" ListName="DocumentType" />
</Field>
Defect ID
To use cross-site lookup you should have Single Line of Text field. That's why you received an error in the field that ad Person or Group type.