There are several reasons why this go around has been wildly inconsistent. The main reason is he hasn't been able to consistently get total buy in from his players and coaches. They were all in early in 2016, they were legitimately a good team then everything changed at Houston. Since that point the team hasn't bought anything the staff is teaching and in some cases the coaches weren't even buying in. While fans are incredibly emotional they know when their team is good and when things aren't right. Once the fans start leaving they are incredibly hard to get back.
I have zero faith in the current assistant coaches. Not one of them has earned their check. I can't think of one unit that has played consistently good since his return. Look each position on offense it all boils down to poor coaching. These all have been consistently happening since his return.
Running backs have fumbled in every game this year
Dropped passes in bunches
Oline missing assignments, consistently getting blown up, and penalties
QB wildly inconsistent in the passing game. All 3 QB has throwing into coverage over and over.
I won't even discuss defense that has been a train wreck which is combination of poor recruiting and coaching. The offense has talent, but coaching is terrible.