Usually DBCC CHECKDB should be executed during off-peak hours.
DBCC scheduled to run off-peak hours
What is type of server? i.e. prod, dev, test?
what is the size of database? Command blocking spid is same as executing? Do you found any error in error log?
~600GB is the size of the DB and the same spid is blocking itself. Of the 17 threads spawned, 7 are blocking itself with the waittype LATCH_EX and the remaining are waiting on CXPACKET
This kind of explains the behaviour. What would be the work around apart from waiting the 20+ hours?