The problem must be in the particular user tough from the calls of the stack its not clear what is the problem happening to this user. The method where the problem occur (ItemsListBase.ConstructDialog) builds the 7 different dialogs that make the grid of uploaded documents shown when accessing Content->Documents & Files module tough there are no security checks there for the problem to be connected with the user role so the user have to do with the problem. I doubt the problem you experience is occurring in sitefinity 5.x versions and its possible to be occurring in earlier version. I see there is a support ticket for the problem where we will need to check the project files for better investigation on the cause of the problem and fix.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items