Error when opening Project Server task with attached document

The following error message comes up in Project Server when opening a task which has a document attachment:

System.Web.Services.Protocols.SoapException: ProjectServerError(s) LastError=GeneralUnhandledException Instructions: Pass this into PSClientError constructor to access all error information
at Microsoft.Office.Project.Server.WebService.PWA.StatusingReadWssLinksForTask(Guid projectUid, Guid taskUid) at Microsoft.Office.Project.Server.WebServiceProxy.PSIProxyBase.InvokePSI(String serviceName, String methodName, Object[] parameters)
at Microsoft.Office.Project.Server.WebServiceProxy.PWA.StatusingReadWssLinksForTask(Guid projectUid, Guid taskUid)
at Microsoft.Office.Project.PWA.ApplicationPages.DetailsPage.InitAttachments()
at Microsoft.Office.Project.PWA.ApplicationPages.DetailsPage.PJWebPage_OnLoad(EventArgs e)
at Microsoft.Office.Project.PWA.PJWebPage.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

The reason for this error is that Project Server apparently can’t handle project task attachments which are not into the “Project Documents” document library. If a document from any other document library is attached to the task then this error is thrown when someone tries to open that task.

So as a workaround, only attach a document to a task if the document is in the “Project Documents” .

UPDATE

Found workaround:

1. Create a Choice column with the name “Status” in the document library
2. Edit the properties of the document that you want to attach, fill the Status field.
3. Documents where the Status field is not empty can be attached to tasks.