What ppqn do you have on the hardware?
Source
.try to change to internal timecode
Destinations
Check all boxes in midi clock destinations
Check all boxes in midi clock preferences
Uncheck all boxes in midi timecode destinations
Check box in midi timecode preferences
Machine control
I have always this uncheck, try with the other settings i give you. And uncheck slav and master here.
but you can try MMC where cubase can only be master and all the other slaves.
So slave you Yamaha. Here are some links under.