I just came to a weird behaviour of the List View-Control in my Nintex Form. I do have a Lookup-Field named "Project" with an additional field "Project:ID" in my list.
In my Nintex Form I added a List View which I wanted to filter to the field "Project:ID" by specified value of the current Item's ID.
If I open the form in preview-mode, I get an errormessage which says "Cannot complete this action. Please try again.".
In the SharePoint-Log the Trace is like following:
Greetings from Nuremberg
If you look at the log, there is one thing that is telling me something (Error=Data at the root level is invalid.)
1.Are you sure that the value type you are using for the lookup is the same type as the value you are filtering on
2.Are you sure that there are no spaces or different characters in the two fields you are using? To test this you can remove the filter for now and try and display the two values with calculated fields on your form.
Greetings from South Africa