Just experienced the same with my G, any tips? - Nout

The issue is it takes a while for the big reeds to stabilize, especially when it's the only one sounding, so you have to provide plenty of bellows travel to give the reed a chance to stabilize to playing pressure. One thing I do is tune the small base reed first, then the big reed, then sound with the smallest reed and biggest reed together. This allows the big reed to stabilize better, and both your ear and and a strobe tuner can pick up the difference, if there is still one.

Yessir that's how I do it