hi Deepak ,
Am facing the same issue but the error is different error " Export Failed : file Content causes system total content length to be exceeded (File content Length : 314 MB ) "
we checked with HP , they recommended to clear the cache but still no use . Please help if you have any solution for it .
sorry for the delay in response , exclude archive reports from the back up if u don't need and then try to export this.
not sure , but u might succeed else suggesting u to contact hp support again for this issue bcz i never come up this type of error.