When the median was being calculated, the division was by the total number of transform data, rather than the selected number of transform data. Under most circumstances this would be the same, but when transforming bezier control points without the handles selected, or when having proportional editing on. This the median calculation would return a wrong result. Note: This problem could occur almost every object type not just Grease Pencil. Resolves: #143534 Pull Request: https://projects.blender.org/blender/blender/pulls/144245