it sounds like a loose connection.you may have a bad pin in the plug where it plugs to the back of the tach,the dealer should have been able to test the regulator hope you aren't paying for the parts swapping.if that plug doesn't stay perfectly tight it won't work,they will corrode up too.
on the other post,,if your engine is over revving your rev limiter will kick in,are you sure the hubs are spun?mark the hub and prop with paint or a small punch in line on each,run it then check it to see if they are still lined up.
most of the time if a hub spins one time and gets hot you can accelerate full throttle on hole shot and it will spin they don't fix themselves,a few times and you can see the rubber messed up if you remove the prop,my uncles vmax was reading 6900 and the dealer sold him a bigger prop,saw him coming,it still messed up and it never hit the rev limiter.