A funny shit happens :( error

[Khranovskiy]

Select 16.1 / 2016.1 and click "Create" btn:

Working copy: 2016.1/Office.GIT
Everything is up to date:
If I select in 17.1 "2017.1.refactoring.." branch - Create btn is working

Khranovsky@khranovsky-w10 MINGW64 /C/Project/2016.1/Office.GIT (2016.1)
$ git st
On branch 2016.1
Your branch is up-to-date with 'origin/2016.1'.
nothing to commit, working tree clean

Khranovsky@khranovsky-w10 MINGW64 /C/Project/2016.1/Office.GIT (2016.1)
$ git lg
* 91c44397 - (HEAD -> 2016.1, origin/2016.1) Move classes from Cell, Range, Worksheet files (Thu Aug 10 12:34:21 2017) <Denis Khranovskiy>
* 2bade23d - [a:yudakov.dmitry t:9] T544002 (Wed Aug 9 15:28:15 2017) <yudakov.dmitry>

Khranovsky@khranovsky-w10 MINGW64 /C/Project/2016.1/Office.GIT (2016.1)
$ git bt
*  (HEAD -> 2016.1, origin/2016.1)
| *  (origin/2016.2)
|/
| *  (origin/2017.1.refactoring.api)
| *  (origin/2017.1)
|/
| *  (origin/2017.2.refactoring.api)
| *  (origin/HEAD, origin/2017.2)
| *  (origin/2017.2.T542072)
| | *  (origin/2017.2.T443525.CopySeveralSheets)
| |/
| | *  (origin/2017.2.CopySeveralSheets)
| |/
| *  (origin/2017.2.T540039)
| *  (2017.2)
|/
*  (origin/master)

2017-08-10 12:35:07,528 ERROR - Unhandled exception, 

System.Exception: The remote server returned an error (422): 
   at NGitLab.Impl.HttpRequestor.Stream(String tailAPIUrl, Action`1 parser)
   at NGitLab.Impl.HttpRequestor.To[T](String tailAPIUrl)
   at NGitLab.Impl.MergeRequestClient.Create(MergeRequestCreate mergeRequest)
   at DXVcs2Git.Git.GitLabWrapper.CreateMergeRequest(Project origin, Project upstream, String title, String description, String user, String sourceBranch, String targetBranch)
   at DXVcs2Git.UI.ViewModels.BranchViewModel.CreateMergeRequest(String title, String description, String user, String sourceBranch, String targetBranch)
   at DXVcs2Git.UI.ViewModels.EditBranchViewModel.PerformCreateMergeRequest()
   at DevExpress.Mvvm.DelegateCommand.<>c__DisplayClass4.<.ctor>b__0(Object o)
   at DevExpress.Mvvm.DelegateCommand`1.Execute(T parameter)
   at DevExpress.Mvvm.CommandBase`1.System.Windows.Input.ICommand.Execute(Object parameter)
   at DevExpress.Xpf.Bars.BarItem.ExecuteCommand(ICommand command, Object commandParameter, IInputElement actualCommandTarget)
   at DevExpress.Xpf.Bars.BarItem.<>c__DisplayClass5a.<OnItemClick>b__59()