Error taking Snapshot during Loadtest

First of all i am using Performance center 12.01

I created a truclient script for firefox with VuGen 12.01. When i am replaying the script with vugen the system is able to take snapshots.

But when i am conducting a load test i get the error message

t=00103891ms: Error -205177: APIError: File_Not_FoundundefinedWhile calling handlers in RuleEngine dispatch, event=[Event type="step/errorSnapshot" target="1: Navigate to TC.getParam("URL")"], handler=function (e) {"use strict";        SnapshotManager.genSnapshotOnErrorFiles(e);    }       Snapshot Info [MSH 4 0]    [MsgId: MERR-205177]    [MsgId: MERR-205177]

and no snapshots are created.In the error message i get the hint that a file is missing but no file name is specified