Hi,
Though, from your post it is visible that you have an error in your response, which itself is not complete.Not exactly, but similar issue occured for me, when only 25% of response data was visible in the GUI. As I used to save all my responses, I notice that all expected response data was available in the saved file.Still i am not able to figure it out the reason for the same, and opened up a case in the forum.My reason for this behaviour says that, could be GUI resposne may not be able to handle big volume of data & thus has its limitation on how much to show from GUI response screen.
In your case,any trace/logs from the application also serves good purpose,if error is user defined.Anyhow, if it occurs for few service alone, as already suggested, you need to be in touch with the service provider.
Thanks
Gurpreet