I know this is somewhat of a boring recommendation, but I'd try a factory reset on the Slingbox. Often, if there is an unusual error like this, resetting will upload the latest "firmware" and resolve these types of issues. I'd also recommend deleting and reinstalling the SlingPlater Desktop App.
Here the steps: Slingbox.com - How to reset your Slingbox to factory settings
Let me know if this helps,