As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) IN LEVEL FLIGHT, THE R/H HSI INTERMITENTLY INDICATED 10 DEGREES NOSE DOWN WITH NO FLAGS SHOWING. SHORTLY AFTER THE UNIT WAS INSTALLED, IT TOOK 20 MINUTES TO SPOOL UP ON ONE LEG BUT THE FAULT COULD NOT BE DUPLICATED. THE VERTICAL GYRO WAS REPLACED AND AIRCRAFT RETURNED TO SERVICE.