Hi David,
I don't believe it has anything to do with bridges being blocked.
Here's what I know: There was a few days downtime at the end of August for the first-listed FTE bridge in the Tor Browser. However, not all FTE bridges listed in the Tor Browser were down at that time. It should have been the case that failover worked properly. So, my guess is that (1) some of the FTE bridges listed in the Tor Browser are not properly reporting stats or (2) failover isn't working properly.
It's on my TODO list to investigate this further.
-Kevin