Im not an expert at sorting through the logs that are available on this device. But seeing as this is an error that takes a month to surface your gonna have a task trying to pinpoint it.
My guess is it would be the USHARE app causing it. Next time the situation arises, log in and disable that module and see if it clears things up. Or try a different Media Server. My guess is he's the culprit but pinpointing a slow growing issue may be hard.