I can't add 2 mm thickness

hi.i try it the Solidify and don’t want to work on my laptop blender 2.9 . PART FROM BUTTERFLY.stl (348.9 KB) . for 2 and 3 mm in Solidify is doing ugly forms. Or can somebody with this raw file SIMPLE PART FROM BUTTERFLY.blend (866.8 KB) . if somebody succeeds, let me know how with a video, step by step how .thanks.