Hmm. Rereading the description, it sounds like maybe the websockets were still getting updates appropriately but for whatever reason the CSRF token was missing from the chart data request? Are you accessing it through a proxy?
Without some clearer direction and it being, "fixed" we're unlikely to keep thinking about it. If you notice it again, be sure to recount what you were doing in the system for some time prior. I would not expect the existence of users to be the affecting factor. If it were, restarting would be sufficient to blow out any caching, and user session information is not stored in the database.