Hi Charlie,
It sounds like permissions or potentially a network issue when connecting to your MSSQL server. The team's Visibility API log ( api.log ) or MSSQL server log may provide a lead in diagnosing the issue further.
Since it seems the issue resolves itself after a few minutes, a network trace may be helpful as well. The above mentioned items may contain sensitive information, so I recommend opening a support ticket for us to troubleshoot further, if necessary.
Matthew Kennedy