As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE INSTRUMENT VACUUM SYSTEM FAILED. THE AIRCRAFT RETURNED TO MAINTENANCE AND AN INSPECTION OF THE SYSTEM REVEALED THAT THE ROTOR SHAFT HAD SHEARED. PROBABLE CAUSE MAY BE THE ENGINE MOUNTS USED ARE TOO SOFT AND ALLOW THE ENGINE TO VIBRATE TOO MUCH AND THIS CAUSES THE PUMP SHAFT TO SHEAR. RECOMMEND ALTERNATIVE DRY AIR PUMP OR ALTERNATIVE ENGINE LOAD MOUNTS.