What do "collapsed" meaning in tor log?

What do “collapsed” meaning in tor log?

Your Guard [scrubbed] is failing a very large amount of circuits. Most likely this means the Tor network is overloaded, but it could also mean an attack against you or potentially the guard itself. Success counts are 52/171. Use counts are 73/76. 164 circuits completed, 1 were unusable, 112 collapsed, and 4 timed out. For reference, your timeout cutoff is 60 seconds.

from:Tor repeatedly tells me that "Your Guard is failing an extremely large amount of circuits" when using snowflake (#23780) · Issues · The Tor Project / Anti-censorship / Pluggable Transports / Snowflake · GitLab