Please check the server machine's Event Viewer
for any error coming from the application. Also verify the application process is not reset e.g. changes in the deployed files, configuration file or assemblies. Place logging where reports are retrieved to check the retrieved collection on each request.
To record requests and their responses you can use Fiddler
running in parallel to the application in browser. In Fiddler - Inspectors - Request/Response - Raw tabs you can see the performed requests and their responses.
I hope the provided information is helpful.
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