Exception thrown when trying to use j.telligent.evolution.post

This works in version 11 but throwing exception in V12

I am trying to do following Post 

j.telligent.evolution.post({
url: j.telligent.evolution.site.getBaseUrl() + 'api.ashx/v2/kmpro_collections/{ApplicationId}/documents/{ContentId}/privatefeedback.json',
data: {
ApplicationId : '$kmp_v1_documents.Application.Id',
ContentId: '$kmp_v1_documents.Current.ContentId',
Subject: j('#$core_v2_widget.UniqueId('feedbackTitle')').evolutionComposer('val'),
Body: j('#$core_v2_widget.UniqueId('feedbackBody')').evolutionComposer('val'),
},
success: function(response) {
jQuery.glowModal.close();
}
});

It throws an exception 

System.MissingMethodException: Method not found: 'System.String Telligent.Evolution.Rest.Extensions.ExtensionsForException.ToUserRenderableMessage(System.Exception)'.
   at Telligent.Evolution.KMPro.Plugins.Rest.DocumentRestRoutes.HandleFeedback(IRestRequest req)
   at Telligent.Evolution.Rest.Framework.Infrastructure.RestPluginHttpHandler.ProcessRequest(HttpContextBase context, HttpResponse httpResponse)