In the current version (2.6.4 (1274)), exporting a single-master glyphs file to UFO results in an error:
Something went wrong while exporting: -[NSSavePanel runModalForDirectory:file:types:relativeToWindow:]: unrecognized selector sent to instance 0x7f8bf2115340
I also notice that when exporting a font with more than one master, the export window cuts off some of the content, although the export seems to work.
I’ve tried this with multiple, unrelated glyphs files, so it’s not specific to one file.