Thanks for the detailed analysis.
I found that there are 2 instances of the stuttering issue. One is triggered by location, and you will consistently get the problem in that location. These bad locations have a problem if you fly into them or if you spawn directly into the area. But you can fly out of the area and things return to normal.
The 2nd is a random stuttering event where it starts in an area that has previously been free from problems. I have found you can’t fly out of these (or if you can, the time required exceeded my patience) and that this requires a MSFS restart to fix. After the restart the same area is free from problems again.
In the recent video Asobo mentioned 2 things they had fixed so far, so I hope it covers both of these.