Thread is becoming too long and I am losing track
You said fermentation took longer than anticipated, right? If that is the case, and you have good control of your oxygenation and fermentation temp, and given that you pitched a lot of yeast, vitality is a likely issue. Sulfide aromas during fermentation also points out to yeast problems as Abbey mentioned.
If I misread your comments and you had a quick fermentation and no sulfide aromas during it, incomplete gelatinization at the beta stage or your beta rest at too high a temperature seem more likely.