run lazarus 1.8.4 for windows, new appliction project, put a groupbox on empty form, set groupbox's propety enabled to false,without change anything else, run it, this problem will shown.
i test two pc, os is all win7 x64 sp1, this problem is same. it use microsoft yahei ui font。
i guess disabled groubox will draw by self, caption shadow distance calc is not right in some place.
lazarus 1.8.4 ide also showing this problem, so i think some code is must be wrong or os have bug?
Graphics.GetFontData(Font.Handle).Name will return unrecognizable characters, for fontname have chinese characters, GetFontData not convert correctly. it use 微软雅黑, equal microsoft yahei ui font.