Interesting. I've not tried NBT through a team before. Although I would also have chosen SLA as the mode most likely to work, have you tried RLB (Recieve Load Balancing)?
SLA load-balances on both transmit and recieve, and I suspect that might be what's killing NBT
I went into the properties of NICs and looked in the settings area of the "Advanced Tab" but see no listings for SLA Load-balances.
Next I clicked on Teaming tab and went into the teaming properties and into the Advanced tab there. I do see one option for Load Balance but not the SLA option. Im thinking Im not looking in the right area.
Im also checking on driver updates (Supermicro support asked me to double check on driver updates)