I have a 1977 Turbo Arrow IIi. 18 months ago the alternator died. Shortly after the new Hartzell alternator was installed, I started getting erratic ammeter indications on some, but not all, of my flights. See the attached videos. When the ammeter falls to 0, the yellow alternator light briefly illuminates and then extinguishes when the alternator comes back on line. Hartzell doesn’t think it’s an alternator issue and my mechanic was unable to find anything wrong during the last annual. Any thoughts would be appreciated.