The hard shutdown on the 19th Aug can't have been the cause if the database backup from the 28th August is undamaged (as you indicated).
When did the job start failing? Look for anything that happened between the last time the integrity job ran successfully and the first time it failed.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability