"ORConn connect failure cache" interferes with "Optimistically retrying bridges"
Tor has an "ORConn connect failure cache", which remembers connection failures to relays, and refuses to connect to those relays during the minute after the failure. We grew this submodule in #24767 (closed) (commit f29d1583, went into Tor 0.3.3.4-alpha) when we noticed that when a popular relay goes down, each EXTEND cell that asks to extend to it results in a new TCP connection attempt, and in the time until clients stop thinking the relay is up, other relays can generate many thousands of connection attempts.
It turns out that our ORConn connect failure cache also caches failures, and blocks reattempts, for when clients attempt to connect to bridges. That is, if you try to connect to your bridge and you fail, and then you try again within a minute, Tor will helpfully refuse to even try, and just mark that connection as a failure (causing you to mark the bridge as down again too).
This is actually potentially a useful feature still. For example, when your bridges are genuinely unreachable, Tor's descriptor fetch retry schedule makes a new connection attempt every 3 seconds or so for the first 30 seconds, and makes something like 15 attempts in the first minute. That's kind of a silly retry rate, and this failure cache prevents clients from actually producing network traffic based on these overeager retries.
But there is one edge case where it is a clear lose: if you go offline, try to connect to your bridge and fail and mark it down and mark yourself offline, and then you come back online soon after and receive a socks request, Tor in circuit_get_open_circ_or_launch() will log about "Optimistically trying known bridges again" and then it will mark all your bridges as maybe up again, to let you try connecting again right then. But if your retry happens within a minute of your failure, the failure cache will kick in, and fail your new attempt, and you'll mark that bridge down and need to wait for that minute to end, and possibly also a new socks request to come in, before you can get unstuck.