As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HYDRAULIC SYSTEM PRESSURE INDICATION: DURING DESCENT INTO IAD AT 29,000', WE NOTICED THAT HYDRAULIC PRESSURE BEGAN TO FLUCTUATE AND WOULD DROP TO ZERO "---". THIS AROUND 1848Z. NO CAS INDICATION AND NO LOSS OF SYSTEMS. CORRECTIVE ACTION: TIGHTENED GROUND ATTACHMENT SCREWS. REPLACED PANEL SCREWS. IAW CE-680A AMM 20-30-00 & 20-10-65