I think it's a mind-set on offense, an inability to continue doing what's working...
Also, when you don't get to the middle of the field much, which tends to have more persistence than throwing deep outs and fly patterns all day, you're going to have issues "cyclically" during a game.
The Bills seem to have ZERO packages for Cover-0 or Blitz schemes, it's just block who you can and chuck it up in time. It's almost like the 98-yard TD pass against the Steelers was a curse-in-disguise, because it worked but has now become the standard vs. developing a more high-% blitz-adjusted passing game.
Where did that WR screen go that they had perfected under Daboll?