Sounds like it may be periodically failing an authentication check back to Bungie. Note this gets routed along the west coast in the US, so it may be a long trek for a lot of people. Where are you and what ISP do you use? Been seeing reports from several regions facing high congestion and other stability issues typically bound to their ISP or at the peering level (additional ISP's involved in the routing). Such things fall to those ISP's for resolution.