This happens to me if I do the following:
I import an image in lightburn, rotate it.
Then I right-click and adjust image.
You can see that on left sample it is still not rotated, and in the right sample it is rotated but with a deformed size
It appears to only be a problem with the Preview window in the Adjustment Dialog box.
If you allow the adjustment and then Preview in the main program, the adjustments are applied without the distortion being visible.
Agree, this would certainly not be what I would expect either. Hard to tell just how the adjustments are affecting the selected outcome so not much value until this is fixed (at least for rotated images).