Sorry for the thread being so convoluted, so for clarification purposes;

Post 1: first video current wayward handling.

Post 4: second video shows non-functioning right rear shock due to top mount coming undone, the car weaves but has an up and down motion to the oscillation dissimilar to the video in post 1.

Post 8: video of car pre-oscillation issue, same exact set up but with H145 rear end, problem started with the install of the H190.

So to surmise; first video shows current issue, second video shows what it looks like with no damping, third video shows how it was before this issue. Binding tends to be snap oversteer / opposite lock, car weaves all by itself without any steering correction. So I’d say no binding. The car behaves & feels different now versus known condition with 0 damping. So I’d say shocks not likely cause.

The left side rear axle has 6-8 thousands of end play (haven’t checked right but expect the same).
So the question now would 16 thousandths / 1/64” of end play cause the car to weave back and forth as it does in the first video?

If I’m visualizing this correctly; in a corner the outside axle would push in and the inside axle would pull out, the rear track would be 1/64” inside of the front track. The rear would move toward the outside to correct the dog tracking, this would cause oversteer / rear steer, which intern would lower the lateral force which may in turn cause the axles to move again, hence the tank slapper.

This vigorous back and forth action also likely explains the bizarre wear pattern on the rear tires.

In a previous post I noted the inside edge of tires looked like someone took a woodworkers gauge to the inner most tread block.