ive got a similar problem, mine does it at 5k though
So far ive tried cleaning the connections on the coil and ive tried some more dash clocks but the problem still persists
Ive got a homemade earth point on my rev counter that i found when i removed the clocks so am going to fix this, i have a spare coil to try at some point as well
If you find out what it is then let me know