Thread is becoming too long and I am losing track
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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.