What version are you running?
3.0.10
What's the URL of the page containing the problem?
/r/{id}
What steps will reproduce the problem?

Create a review request
As admin, grant all permissions to review requests, diffviewer and drafts for other user
Log in to another user (with permissions)
Upload new diff to the review request


What is the expected output? What do you see instead?
Green div informing that review request is a draft should be displayed. Instead there is not even any info about diff being successfully uploaded, and user with permissions can't update the review request from web app.
What operating system are you using? What browser?
OS and browser independent
Please provide any additional information below.
Publishing draft through API/rbt is workaround for this problem but it's very inconvenient to manually send requests to API every time you want update the review request of which you are not owner. Fact that user can publish draft through API proves that it's not a permissions issue.
tl;dr
User can't publish review request draft from browser. He is not an owner of a review request, but he has permission to do that.