Hello,

Thank you for bug reporting.

Unfortunately this is really a bug :-( But I can give you some workaround how to solve the problem. Please follow instructions bellow:

1) Please open '<web project>/CMSWebParts/Viewers/cmsrepeater.ascx.cs' file in Visual Studio.

2) Please find following line (most probably on line 784):
this.btnAdd.Path = DataHelper.GetNotEmpty(mPath, "");

3) And modify it like this:
this.btnAdd.Path = CMSContext.ResolveCurrentPath(DataHelper.GetNotEmpty(mPath, ""));

This should enforce appearance of 'Add new item' button using your path expression.

Anyway it will be fixed in next version of Kentico CMS 3.1a, which should releases hopefully within few days.

Best Regards,
Ondrej Vasil