Thanks guys, a lot of the stuff seems to be fixed, although building diacritics with components using anchors seems broken to me now (in the most recent bleeding edge Glyphs 1 version).
I added the required anchors in the baseglyph called “top” and in the accent “_top”. It does not make a difference to me if I “generate glyph” or try to rebuilt with components, Glyphs 1.4.5 (614) seems to ignore the anchors and just pastes the components in there.
PS: Glyphs manages to preview the component’s position when moving the anchor in the base glyph, but not in the composed one.
Did you disabled the automatic alignment in Font Info > Other Settings?
I do not recall that I did, but now it works just fine, thanks!