Cannot upload documents in document set with connected web parts

Question

On SP2010 I have a Document set library that leverages several connected web parts. Web part one is a filtered task list based on a page filter. Web part two is a custom list that has a connection to web part one. This part of the page is working fine, when a user opens the doc set the first task is selected and the associated list items from web part two are showing. The user can click on the documents web part and then select the upload documents action from the ribbon without issue.

So here is the problem:

When the user selects task two the correct list items are displayed but they can no longer select upload documents from the ribbon after clicking on the documents web part. The same thing happens when switching back to task one. No matter what I do, I can't get the upload docs to be clickable once a task has been selected after the initial doc set is opened.

Important point

Each document set has permissions broken and only people in the group called Supervisors (contribute access to library) and the individual person can see/contribute to the doc set. Anyone within the Supervisor group can click on the tasks and upload docs without issue. It's only the individuals who are assigned the doc set who this is happening to.

Answer 1

I've figured out the issue with the Upload document action item not always being visible. The users were not granted contributor privileges in the library so even though they were added to the document set as contributors (through workflow), they need to be in the library before they can inherit the security from the document set.