If you are in the documents page and there is an Assessor Document Group, when you click upload you are given the option to upload a document to this group, however, it is not possible to upload a document. You get an error message:
The action cannot be completed
"A Submission must be selected when loading data into this Document Group"
However, you are not given an option to select a submission.
This only happens if the Project Manager also has assessor work. The upload gets blocked (because no submission has been selected), and the system is prevented from getting into an invalid state.
Solution: Uploads to an Assessor Document group should only be made via the question response sheet