When creating a powerclip, transformations from the clip source were not being applied. And when you duplicate an object, the coords of that object will be the same, but just with a transformation applied.
So if you duplicated an object, then used it as a clip source, the inverse clip LPE code was ignoring the transformation and the clip would miss the intended target entirely.
This applies the clip's i2dt_affine() when calculating the inverse clip.
Fixes #6158 (closed)
(As an aside, this kind of thing feels like a foot gun lying around - where you ask an SPShape for its curve, but you secretly also have to know to apply the i2dt_affine if you want the curve in desktop coords. I guess that makes sense - they are two different things, and the rest of the inkscape code seems comfortable grabbing the affine and multiplying in lots of places. But I kinda wish that calling SPShape->curve() took a required enumeration like WITH_TRANSFORMS, WITHOUT_TRANSFORMS - or some other way to force the caller to reckon with the distinction. Any change in that respect felt way out of scope for this bug fix, but just noting it.)