Error reordering backlog priority in TFS2015 - tfs-2015

Question

In TFS at the backlog, you can reorder work items by selecting and dragging items according to the desired order.
When we try to do this with our recent TFS 2015 install, this error pops up:
Which says:
An error has occurred while attempting to save your changes. Click
here to discard your changes and refresh your view of the backlog.
Error details: TF400486: Unable to complete the operation because you
or another user has modified, removed, or re-parented items, or you
are trying to reorder an item outside of its immediate parent.
When we check the event log on the TFS machine, this exception is present:
Microsoft.TeamFoundation.Server.WebAccess.Agile.Models.BacklogChangedException:
TF400486: Unable to complete the operation because you or another user
has modified, removed, or re-parented items, or you are trying to
reorder an item outside of its immediate parent. at
Microsoft.TeamFoundation.Server.WebAccess.Agile.Utility.ProductBacklogReorderHelper.PerformReorder(ReorderOperation
operation, WorkItemData previousItem, WorkItemData nextItem,
WorkItemData reorderItem, List1 workItemsData) at
Microsoft.TeamFoundation.Server.WebAccess.Agile.Utility.ProductBacklogReorderHelper.Reorder(ReorderOperation
reorderOperation) at
Microsoft.TeamFoundation.Server.WebAccess.Agile.Utility.ProductBacklogReorderHelper.<Reorder>b__0(ReorderOperation
o) at System.Linq.Enumerable.<SelectManyIterator>d__142.MoveNext() at
System.Linq.Enumerable.d__811.MoveNext() at
System.Collections.Generic.List1..ctor(IEnumerable1 collection) at
System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at
Microsoft.TeamFoundation.Server.WebAccess.Agile.Controllers.ApiReorderWorkItemsController.ReorderWorkItems(ReorderOperation[]
operations, String hubCategoryRefName, String iterationPath) at
lambda_method(Closure , ControllerBase , Object[] ) at
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext
controllerContext, IDictionary2 parameters) at
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext
controllerContext, ActionDescriptor actionDescriptor, IDictionary2
parameters) at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass42.b__41()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.<>c__DisplayClass39.b__33()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.b__49()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.b__36(IAsyncResult asyncResult) at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<>c__DisplayClass2a.b__20()
at
System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.b__22(IAsyncResult
asyncResult) at
System.Web.Mvc.Controller.<>c__DisplayClass1d.b__18(IAsyncResult
asyncResult) at
System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.b__3(IAsyncResult
ar) at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult
asyncResult) at
System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.b__3(IAsyncResult
ar) at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)
at
System.Web.Mvc.MvcHandler.<>c__DisplayClass8.b__3(IAsyncResult
asyncResult) at
System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.b__3(IAsyncResult
ar) at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult
asyncResult) at
System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step,
Boolean& completedSynchronously)
What steps should we take to resolve this?

Answer 1

You can try:
upgrade TFS 2015 to TFS 2015 Update 1.
clean the file cache folder on your AT machine: C:\TfsData\ApplicationTier_fileCache
restart the TFS application pool in IIS.

Answer 2

As it turns out, this was related to how we used TFS in the past versus TFS now.
The guidance here indicates that work item ordering should be done in the context of features.
That is, order by feature, then in the relevant Sprint backlog, order by the work items present.

Answer 3

I noticed this only happens if:
CASE 1:
I move a PBI with children and put it before another PBI or
CASE 2:
I move a PBI and put it after a PBI with children
The workaround I used for each case is this.
WORKAROUND:
Imagine this is the order:
PBIWithChildren
PBINoChild
PBIINeedToMove
and this is the order I want to achieve:
PBIINeedToMove
PBIWithChildren
PBINoChild
I moved PBIWithChildren one down. So the order became like this:
PBINoChild
PBIWithChildren
PBIINeedToMove
Then I moved PBIINeedToMove and dropped it before PBINoChild so the order became like this:
PBIINeedToMove
PBINoChild
PBIWithChildren
Then I moved PBIWithChildren one up and ended with this which is what I wanted to achieve:
PBIINeedToMove
PBIWithChildren
PBINoChild
I know that sounds like many steps but only when you need to write it. Otherwise, it is a quick workaround.

Answer 4

I just ran into this issue and resolved it by ensuring my feature iteration path was in the same iteration path assigned to the corresponding team's backlog. This may not work in all cases but after making the change I was able to reorder my features with their children without error.

Answer 5

We experienced the same issue.
In our case, the error was caused by an accidental linking between features and requirements within a teams backlog:
A requirement, which already had a parent, had been made the parent of a different feature. Hence ordering of the backlog was no longer possible.
So in order to resolve this, we had to find the requirement, which had been made a parent of a different feature and remove this parent/child link. We were then able to reorder the requirement backlog.

Answer 6

This is still happening in VSTS on the Kanban board at the Stories level. I was able to work around this problem by moving a user story to a different column then moving it back to the original column in the order I desired. Annoying, but it seems to work.

Answer 7

Just to add to the list of experiences, I have just come across this in TFS 2018.1.
In my case, it occurred after one of our teams reorganised the way they were using boards, and made some sweeping changes to the area and iteration paths on PBIs, but not on tasks.
The root cause was that some (preexisting) open (New, Inprogress) tasks under the PBI were in a different iteration and area to new tasks added. Ensuring all open tasks were in the same areapath/iteration resolved the issue.

Answer 8

In my case, I had a features backlog view that choked. I discovered I had user stories as parents of bugs, which were set to be at the requirement level and not the task level (meaning they were nested). Fixing the bug/user