Ssparky, I don't think you have a midi problem.
I think it is a chord recognition problem on the Tyros.
Check to see the mode on the Tyros, could it be a one finger recognition, or piano style?
Go thru your choices till you get a match to the Ketron.

The above is if you are using the arranger features of the Tyros.
If you are using the Tyros sound only, make sure you turn off the arranger receive channel on he Tyros.