Hey Mike,
On your next two flights, try and keep the speed always below red or red-stripe.
I am still suspecting we create damage to the trim that is causing the dutch-roll/oscillation. If there “is” damage we can’t see it but the plane is designed to react to the damage…
It’s still a theory on my part. You have to watch your speed in this bad boy because it goes up so fast. Hopefully, this will resolve it for you!