Upload coauthors removed unexplicably

@g-michaelgoette reported that on their Oasis (1.3.15 release) an upload was shared with groups and people as coauthors but then it was only shared a single person.

Steps to reproduce (source)

1. add a bunch of users as authors/reviewers to an upload
2. wait for 6-12h (i think there is some server caching somewhere)
3. share the upload with a new person quickly, before the full list of coauthors is shown
4. hit submit

directly after adding 100 users they where loaded in 0.2 sec to quick to add a user, but in the evening it took multiple seconds enough to search and add a new author.