Is NextBus starting to fail in Boston?

This past month or so, I've started to notice that, from time to time, a bus will pass by without appearing on my NextBus GPS-tracking feed. At first it was just once in a while, enough to make you start wondering, but not terrible. Today, I spotted two buses that never appeared on the tracking. In addition, in the evening rush hour, the feed only showed buses arriving in 24 and 96 minutes -- this on a key route which runs every 10 minutes all day. Something weird is going on. I am presuming that the GPS units inside of the buses are failing in some fashion.

I haven't had an experience as bad as these ghost buses in D.C. with NextBus in Boston. Actually, the service has been pretty good so far. It's a little optimistic about the speed of MBTA buses, so sometimes that last "1 minute" takes longer than one minute. I hope that this is just a temporary glitch. The real-time data really changed the way I used public transportation, making it a lot more convenient, and a lot less stressful.