Do you by any chance have an engine monitor that records parameters? I would look back at the oil pressure during the anomaly. Years ago, I had the same thing happen when the line from the proper governor to the hub failed.
At the time I took my IFR ride a couple years ago I had a Garmin 430W and an STEC 30 with GPSS. I recall I did two of the three approaches using the auto pilot and probably a bit more than half of the total ride. I clearly remember hand flying one VOR approach. The examiner did not attempt to...
70 back in November 2020. Almost exactly 20 years after passing my PPL. Tremendous feeling of accomplishment. And I have stayed IFR current since then in my Arrow.