Does this happen only with snowflake, or non-snowflake?
I'm in a censored area for the moment so I can't answer that question (meek is a no-no since it's too damn slow).
One note though: It's not an issue with the snowflake server since all it takes for me to get Tor working again is to just restart the browser and then it immediately works again.
Deferring 51 tickets from 0.4.0.x-final. Tagging them with 040-deferred-20190220 for visibility. These are the tickets that did not get 040-must, 040-can, or tor-ci.
Adding the "snowflake" keyword because while this situation can arise with any kind of transport/bridge, it's more likely to happen with snowflake because snowflake is more likely to drop connections and make tor think its connection is unreliable.
I don't think this is a regression; I've managed to get tor into a loop of Delaying directory fetches: No running bridges many times in the past while testing other pluggable transports. It's likely that the preceding log message was
[warn] Your Guard flakey ($2B280B23E1107BB62ABFC40DDCC8824814F80A72) is failing an extremely large amount of circuits. This could indicate a route manipulation attack, extreme network overload, or a bug.