Android Camera2 why do the proportions of my preview change after rotation followed by rotation back?

In my app I have a camera preview on a SurfaceView and it is working almost exactly as I want it to, with one weirdly annoying problem:

When I enter camera view on my Sony Xperia or my testing Samsung S7 ( the emulator seems fine ) it shows the preview correctly. When I rotate it, the preview rotates correctly, when I rotate it back, the preview loses it's proportions and the view is distorted. After the first rotation, every time it rotates back I have that same distortion.

The approach that works so far is that I use scaling of my SurfaceView:

    FrameLayout.LayoutParams newScale = new FrameLayout.LayoutParams(width, height, Gravity.CENTER );
    mTextureView.setLayoutParams(newScale);
    mTextureView.setScaleX( xScale);
    mTextureView.setScaleY( yScale);

Then I create the captureSession:

  mCaptureSession = cameraCaptureSession;
            try {

                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

               mPreviewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, cropRectangle);
                mPreviewRequest = mPreviewRequestBuilder.build();
                mCaptureSession.setRepeatingRequest(mPreviewRequest, getCaptureCallback(), mBackgroundHandler);
            } catch (CameraAccessException e) { 
                // and so on.
            }

Obviously by this point I have got pretty frustrated, so I have been logging the heck out of my rotations and this is where I am getting super-confused.

This looks fine:

========================
View Dimensions (720, 1184)
Sensor Dimensions: (3984, 5512)
Final size: 720, 1280
========================
View ratio: 1.7777778 previewRatio: 1.6444445 scale: 1.0
Image preview size is (720, 1184) scale is: (1.0) image size is (720, 1280)
Image scale is (1.3835341, 0.925) Max Image is (3984, 5512) cropRectangle is (441, 0 -> 3543, 5512)

Then I rotate it:

========================
View Dimensions (1184, 720)
Sensor Dimensions: (5512, 3984)
Final size: 1280, 720
========================
View ratio: 0.5625 previewRatio: 0.6081081 scale: 1.0
Image preview size is (1184, 720) scale is: (1.0) view size is (1280, 720)
Image scale is (0.925, 1.3835342) Max Image is (5512, 3984) cropRectangle is (0, 441 -> 5512, 3543)

Now I rotate it back:

========================
View Dimensions (720, 1184)
Sensor Dimensions: (3984, 5512)
Final size: 720, 1280
========================
View ratio: 1.7777778 previewRatio: 1.6444445 scale: 1.0
Image preview size is (720, 1184) scale is: (1.0) view size is (720, 1280)
Image scale is (1.3835341, 0.925) Max Image is (3984, 5512) cropRectangle is (441, 0 -> 3543, 5512)

Those scales and that crop rectangle look absolutely identical to me, but for some reason the last image is distorted way wider, as though the x-scale was closer to 1.8 or similar. I can rotate back to landscape in either direction and it looks fine, then turn back to portrait and everything is fat again.

I'm wondering whether this is a characteristic of the camera trying to auto-correct but I'm getting short on ideas about how to troubleshoot this further. How can I persuade my phone that having been rotated twice it should show the same proportions that it showed me in the first place?

Update: If I use setXScale and set it to 1.0 on the second run instead of the value it had on the first, it looks correct. But when I compare the transformation matrix of the SurfaceView when the image proportions are bad and when they are good, they are identical, so this looks like a compensation for the bad scaling in the preview. I can change the way the scaling behaves so the initial preview is too narrow and the proportions are correct after rotation, but again this doesn't really help because I need to be able to swap between portrait and landscape without the image being warped by it, which seems as though it should be the default behaviour. Opening the view in Landscape behaves in much the same way - distorted when it is first opened, then fine.

The CaptureSession appears to be re-created correctly each time.

from Android Camera2 why do the proportions of my preview change after rotation followed by rotation back?