This issue also applies when using an *origin anchor to construct non-mark glyphs. Say I have a glyph /_part.aArc for the top-curve of /a and place an *origin anchor in the bottom right of the curve.
The /adieresis is a component glyph which uses /a and /dieresiscomb. All looks fine within Glyphs, but on export the /adieresis is shifted.
Test-file: Test.glyphs (7.5 KB)