Superasymmetry painting shadow does not resize

When enlarging the Superasymmetry painting with the square bracket key, the shadow does not resize along with the painting itself. Aside from being cosmetically weird, this limits the placement of the painting on the wall, as the shadow effectively expands the painting's vertical footprint (i.e. the shadow can't be placed below floor level). Thus, the bigger the painting gets, the higher up on the wall it has to sit.

I found an old thread in the archive where this bug was noted in 2015, but it appears never to have been fixed (or it was fixed and broke again).