So there is a socket timeout with the Ajax client, if the QVS does not respond to the web server within the setting time, default is 60 seconds, the session will 'reset/reconnect', this goes for long running calculations once in the application as well, so you may need to increase the SocketTimeOutInSeconds setting to a higher value, about the best I have given the limited info, if you can provide screenshots or logs, may be able to do some further digging into things.
Here is an article for the setting change:
I would try that and let us know if it works or not.
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