Alfine 8 gear crunch
I'm not sure what kind of 'crunch' you experience, but I have a possibly similar behavior of my Alfine 11 hub when I switch gears and I apply some force on the pedals.

Resting my foot on the pedal while standing and shifting is enough for the internal gears to not complete the shift, when I start pedaling, the gears engage in the speed I shifted giving a noticeable crunching noise.