I am afraid I have to report a bug when generating fonts, TTFs.
It is OK in Glyphs Version 2.4.1 (983), so I can continue work. But Version 2.4.2 (1056) has the problem.
For making OTL tables I use my own tools, so I am not an expert on feature file format, but when I compare the files from the two Glyphs versions, I can see the problem.
I presume I have to mail the file, unless this is something that has been discovered and fixed already.
Best regards, Jelle