Stranger than fiction an exception in the logs which reads
".pyIDUnexposed properties cannot be selected for classes mapped to external tables"
appears quite a handful.
After digging a bit found that i had turned "include all descendant classes" in the reporting on descendant classes - Data Access tab of the report definition. This one didn't elude me much. Am glad i cracked it before it could.
***Updated by moderator: Lochan to update platform capability***