Focus Trend LZ, rear end shaking, bounching

[Dpm]

Focus Trend 2016 (Oct build) registered June 17
LZ - 6 speed manual

(Issue happened at 2100klm mark)

3 months ago I bought the new Focus from a dealer here in Melbourne.

It has been fine, however i just experienced something that concerns me, and wonder if its part of the issues re transmission recently brought to light in the media. However i think those issues only relate to the auto, not the manual i have and to earlier models?

Driving down Rind Road here in Melb, on a smooth as silk piece on road, i had to drop down to 30 k, then going up to 40k in 3rd gear the car started bouncing. It seemed to come from rear, maybe.

I was in seat bobbing up and down like there were corrugations running across the road. The bobby up and down was smooth, no gerking, there was no sounds rattles from anywhere, motor running fine etc.

Then still at 40k in 3rd the bouncing seemed to stop but then the back started shaking from side to side, like the rear wheels were lose and about to fall off.

I then changed into 4th around 45 k and the shaking stopped instantly, and it was all back to normal again.

All this from start till end was around under one minute.

The car other than this moment runs dead straight, as it did while it happened, the steering wheel has no shaking, the car has felt compleatly normal, its just been that one instant.

And since that moment its been fine again, 300k later. I have tried to make it do it again, without success.

It happened at the 2100klm mark, so almost ready to take in for the first dealer 3000klm check.

So like to know what people may think before i get the usual dealer run around.

The car has not hit any pot holes been off road etc, so its not wheel alignment or the like.

I am wondering was it the sensor for towing trailers, as in anti trailer shake mode kicking in when shouldn't have. (no i was not towing).

Any help thoughts welcomed.
Dpm