Tor keeps on trying the same overloaded guard over and over
When Tor can't download microdescriptors (legacy/trac#21969 (moved)), maybe it should try authorities or fallbacks (legacy/trac#23863 (moved)), before it runs out of microdesc retries (legacy/trac#24113 (moved)).
But even after Tor has the microdescs it needs, it sometimes doesn't start building circuits again. Instead, it is in state "waiting for circuit".
For the log messages, see: https://trac.torproject.org/projects/tor/ticket/21969#comment:82